Overexpression of Bcl-2 by activated human hepatic stellate cells: resistance to apoptosis as a mechanism of progressive hepatic fibrogenesis in humans

MicroRNA-130a and -130b enhance activation of hepatic stellate cells by suppressing PPARγ expression: A rat fibrosis model study

Hepatic stellate cells (HSCs) are the primary sources of extracellular matrix (ECM) in normal and fibrotic liver. Peroxisome proliferator-activated receptor gamma (PPARγ) maintains HSCs in a quiescent state, and its downregulation induces HSC activation. MicroRNAs (miRNAs) can induce PPARγ mRNA degradation, but the mechanism by which miRNAs regulate PPARγ in rat HSCs is unclear. This study aimed to investigate some miRNAs which putatively bind to the 3'-untranslated region (3'-UTR) of PPARγ mRNA, and increase expression of ECM genes in rat HSCs. In carbon tetrachloride injection (CCl4) and common bile duct ligation (CBDL) liver fibrosis models, miRNAs miR-130a, miR-130b, miR-301a, miR-27b and miR-340 levels were found to be increased and PPARγ expression decreased. Overexpression of miR-130a and miR-130b enhanced cell proliferation by involving Runx3. MiR-130a and miR-130b decreased PPARγ expression by targeting the 3'-UTR of PPARγ mRNA in rat HSC-T6 cells. Transforming growth factor-β1 (TGF-β1) may mediate miR-130a and miR-130b overexpression, PPARγ downregulation, and ECM genes overexpression in cell culture. These findings suggest that miR-130a and miR-130b are involved in downregulation of PPARγ in liver fibrosis.

Pathophysiology of Liver Fibrosis

Progressive accumulation of fibrillar extracellular matrix (ECM) in the liver is the consequence of reiterated liver tissue damage due to infective (mostly hepatitis B and C viruses), toxic/drug-induced, metabolic and autoimmune causes, and the relative chronic activation of the wound-healing reaction. The process may result in clinically evident liver cirrhosis and hepatic failure. Although cirrhosis is the common result of progressive fibrogenesis, there are distinct patterns of fibrotic development related to the underlying disorders causing the fibrosis. These different patterns of fibrogenic evolution are related to different factors and particularly: (1) the topographic localization of tissue damage, (2) the relative concentration of profibrogenic factors and (3) the prevalent profibrogenic mechanism(s). The mechanisms responsible for the fibrogenic evolution of chronic liver diseases can be summarized in three main groups: chronic activation of the wound-healing reaction, oxidative stress-related molecular mechanisms, and the derangement of the so-called 'epithelial-mesenchymal' interaction leading to the generation of reactive cholangiocytes and peribiliary fibrosis. Most of the knowledge on the cell and molecular biology of hepatic fibrosis derives from in vitro studies employing culture of activated hepatic stellate cells isolated from rat, mouse or human liver. It is now evident that other ECM-producing cells, i.e. fibroblasts and myofibroblasts of the portal tract and circulating 'fibrocytes', are likely to contribute to liver fibrosis. More recently, the attention is progressively shifting to the profibrotic microenvironment of the liver with increasing interest for the role of immune cells and specific subsets of macrophages regulating the progression or the regression of fibrosis, the role of intestinal microbiota and the influence of tissue stiffness. Other major areas of development include the role of tissue hypoxia and the establishment of an anaerobic proinflammatory environment and the influence of epigenetic modification in conditioning the progression of fibrosis.

Potent effects of dioscin against liver fibrosis

We previously reported the promising effects of dioscin against liver injury, but its effect on liver fibrosis remains unknown. The present work investigated the activities of dioscin against liver fibrosis and the underlying molecular mechanisms. Dioscin effectively inhibited the cell viabilities of HSC-T6, LX-2 and primary rat hepatic stellate cells (HSCs), but not hepatocytes. Furthermore, dioscin markedly increased peroxisome proliferator activated receptor-γ (PPAR-γ) expression and significantly reduced a-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), collagen α1 (I) (COL1A1) and collagen α1 (III) (COL3A1) levels in vitro. Notably, dioscin inhibited HSCs activation and induced apoptosis in activated HSCs. In vivo, dioscin significantly improved body weight and hydroxylproline, laminin, α-SMA, TGF-β1, COL1A1 and COL3A1 levels, which were confirmed by histopathological assays. Dioscin facilitated matrix degradation, and exhibited hepatoprotective effects through the attenuation of oxidative stress and inflammation, in addition to exerting anti-fibrotic effects through the modulation of the TGF-β1/Smad, Wnt/β-catenin, mitogen-activated protein kinase (MAPK) and mitochondrial signaling pathways, which triggered the senescence of activated HSCs. In conclusion, dioscin exhibited potent effects against liver fibrosis through the modulation of multiple targets and signaling pathways and should be developed as a novel candidate for the treatment of liver fibrosis in the future.

Antifibrotic effects of luteolin on hepatic stellate cells and liver fibrosis by targeting AKT/mTOR/p70S6K and TGFβ/Smad signalling pathways

BACKGROUND & AIMS

Luteolin has been reported to exert antifibrogenic effects in CCl4 -induced hepatic fibrosis in mice. However, limited information is available on the cellular and molecular events responsible for this effect. This study focused on the action of luteolin on hepatic stellate cells (HSCs) and the relevant signalling molecules and pathways as well as the antifibrotic efficacy in multiple models of fibrosis.

METHODS

The in vitro effect of luteolin on rat HSCs and HSC-T6 cells was assessed using proliferation assays, invasion chamber, quantitative real-time PCR analysis and Western blotting. The in vivo effect of luteolin on progression of fibrosis was assessed in three experimental rat models induced by CCl4 , dimethylnitrosamine (DMN) and bile duct ligation (BDL).

RESULTS

Luteolin inhibited proliferation, migration, collagen synthesis as well as expression of fibrosis-related genes in the activated HSCs and HSC-T6 cells stimulated with or without transforming growth factor-β1(TGFβ1) or platelet-derived growth factor (PDGF). Luteolin induced HSC apoptosis associated with the increased caspase 3 activity and p53 expression, and induced G1 arrest with the decreased expression of bcl-2, Cyclin E and p-Cdk-2. Moreover, luteolin significantly inhibited PDGF and TGFβ1-simulated phosphorylation of AKT and Smad pathway. In vivo study showed that luteolin administration markedly alleviated hepatic fibrosis along with reduced elevations of alanine aminotransferase and aspartate aminotransferase. HSCs were found to undergo apoptosis and decreased expression of p-Smad2 and p-AKT in luteolin-treated animals.

CONCLUSIONS

This study demonstrates that luteolin prevents the progression of liver fibrosis through multiple mechanisms and indicates that luteolin has potential for effective treatment of liver fibrosis.

MicroRNA-155 attenuates activation of hepatic stellate cell by simultaneously preventing EMT process and ERK1 signalling pathway

BACKGROUND & AIMS

Epithelial-mesenchymal transition (EMT) process and extracellular signal-regulated kinase 1 (ERK1) signalling pathway play pivotal roles in hepatic stellate cell (HSC) activation, which is associated with the altered expression patterns of microRNAs (miRNAs). miR-155 is considered a typical multifunctional miRNA to regulate many biological processes. However, little attention has been given to the contributions of miR-155 to simultaneous regulation of EMT process and ERK1 pathway during HSC activation.

METHODS

Differential expression of miR-155 was assessed in activated HSC, sera and liver tissues from cirrhotic patients. Whether miR-155 could directly interact with 3'-untranslated region (3'-UTR) of T cell factor 4 (TCF4) and angiotensin II receptor type 1 (AGTR1) respectively was detected by luciferase reporter assay. The effects of enhanced miR-155 on EMT process and ERK1 pathway, cell apoptosis in HSC activation were also evaluated.

RESULTS

A significant decrease in miR-155 expression was observed in activated HSC, sera or liver tissues of cirrhotic patients. MiR-155 was found to simultaneously interact with 3'-UTR of TCF4 and AGTR1 mRNAs, which are known as important regulators associated with EMT and ERK1 pathway repectively. Inhibiting miR-155 expression could stimulate the EMT state and ERK1 pathway activity, thus contributing to HSC activation. Forced miR-155 expression markedly decreased the mesenchymal markers and phosphorylated ERK1 level, and enhanced E-cadherin expression, leading to the synchronous inhibitory effect on EMT and ERK1 pathway and inducing HSC apoptosis.

CONCLUSIONS

Our results implicate that miR-155 plays an important role in regulating the pathological network involving EMT process and ERK1 pathway during HSC activation.

Hepatic fibrosis: Concept to treatment

Understanding the molecular mechanisms underlying liver fibrogenesis is fundamentally relevant to developing new treatments that are independent of the underlying etiology. The increasing success of antiviral treatments in blocking or reversing the fibrogenic progression of chronic liver disease has unearthed vital information about the natural history of fibrosis regression, and has established important principles and targets for antifibrotic drugs. Although antifibrotic activity has been demonstrated for many compounds in vitro and in animal models, none has been thoroughly validated in the clinic or commercialized as a therapy for fibrosis. In addition, it is likely that combination therapies that affect two or more key pathogenic targets and/or pathways will be needed. To accelerate the preclinical development of these combination therapies, reliable single target validation is necessary, followed by the rational selection and systematic testing of combination approaches. Improved noninvasive tools for the assessment of fibrosis content, fibrogenesis and fibrolysis must accompany in vivo validation in experimental fibrosis models, and especially in clinical trials. The rapidly changing landscape of clinical trial design for liver disease is recognized by regulatory agencies in the United States (FDA) and Western Europe (EMA), who are working together with the broad range of stakeholders to standardize approaches to testing antifibrotic drugs in cohorts of patients with chronic liver diseases.

NGF and P75NTR gene expression is associated with the hepatic fibrosis stage due to viral and non-viral causes

This study evaluated the relative mRNA expression levels of nerve growth factor (NGF) and the p75 neurothrophin receptor (p75^NTR) in different histological stages of human liver disease. Fifty-one liver biopsy specimens obtained from patients with hepatitis B virus (n = 6), hepatitis C virus (n = 28), and non-viral hepatitis – (n = 9) and standard histological liver (n = 8) as controls (CT) were subjected to qPCR and histopathological exams. Our data revealed a significant difference in the NGF expression levels between the three patient groups and the Control group. p75^NTR expression levels in the HCV and NVH groups were higher than those observed in the HBV and Control groups. In cases of liver cirrhosis, higher p75^NTR mRNA expression was observed, whereas NGF was expressed at higher levels in patients with hepatic fibrosis. NGF expression was lower in the F1 liver fibrosis stage, and p75^NTR receptor expression continuously and proportionately increased compared to the increase in the degree of fibrosis and was significantly higher in livers in fibrosis stages 3 and 4. The hepatic levels of NGF and p75^NTR were decreased and increased, respectively, relative to the stage of inflammatory activity. A positive correlation between p75^NTR and NGF gene expression was observed in livers with mild to moderate fibrosis, though not in cases of severe fibrosis and cirrhosis.

Neuroinflammatory Mechanisms of Connective Tissue Fibrosis: Targeting Neurogenic and Mast Cell Contributions

Significance: The pathogenesis of fibrogenic wound and connective tissue healing is complex and incompletely understood. Common observations across a vast array of human and animal models of fibroproliferative conditions suggest neuroinflammatory mechanisms are important upstream fibrogenic events. Recent Advances: As detailed in this review, mast cell hyperplasia is a common observation in fibrotic tissue. Recent investigations in human and preclinical models of hypertrophic wound healing and post-traumatic joint fibrosis provides evidence that fibrogenesis is governed by a maladaptive neuropeptide-mast cell-myofibroblast signaling pathway. Critical Issues: The blockade and manipulation of these factors is providing promising evidence that if timed correctly, the fibrogenic process can be appropriately regulated. Clinically, abnormal fibrogenic healing responses are not ubiquitous to all patients and the identification of those at-risk remains an area of priority. Future Directions: Ultimately, an integrated appreciation of the common pathobiology shared by many fibrogenic connective tissue conditions may provide a scientific framework to facilitate the development of novel antifibrotic prevention and treatment strategies.

A morphologic and semi-quantitative technique to analyze synthesis and release of specific proteins in cells

BACKGROUND

With the rapid advancement of cell biology, the evaluation of a given protein's synthesis and release in cells becomes critical. However, up to now there has been no technique available to morphologically visualize and measure a newly synthesized protein in cells, nor can we measure the protein's release from the cells.

RESULTS

In this study, we developed a set of assays combining pulse chase amino acid substitution, non-radioactive labeling, and immunofluorescence co-localization to visualize newly synthesized proteins in individual cells and then to detect their release using modified ELISA. We demonstrated the synthesis and release of Bcl-2, MMP-9, and immunoglobulin G (IgG) in a human trophoblast cell line, of which the last finding has not been reported previously.

CONCLUSIONS

This new technique offers a powerful tool to evaluate the dynamics of the synthesis and release of target proteins in individual cultured cells with wide applications in genetic and protein analysis.

Curcumol induces HSC-T6 cell death through suppression of Bcl-2: involvement of PI3K and NF-κB pathways

The major feature in the molecular pathogenesis of hepatic fibrosis requires maintenance of the activated hepatic stellate cells (HSCs) phenotype by both proliferation and inhibition of apoptosis. Thus, the induction of activated HSCs apoptosis has been proposed as an antifibrotic treatment strategy. Curcumol has pro-apoptotic activity in a number of cancer cell types. The aim of this study is to test the hypothesis that the interruption of the phosphatidylinositol 3 kinase (PI3K)/nuclear factor-κB (NF-κB) signaling pathway by curcumol might induce apoptosis of activated HSCs. Our results indicated that curcumol-induced growth inhibition correlated with apoptosis induction as evidenced by Annexin V staining, and cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP) in HSC-T6. Importantly, we show that the apoptotic effect of curcumol was specific to the activated HSCs (HSC-T6). Suppression of the NF-κB translocation via inhibition of IκB-α phosphorylation by the curcumol led to the inhibition of expression of NF-κB-regulated gene, e.g. Bcl-xL and Bcl-2, in a PI3K-dependent manner, which is upstream of NF-κB activation. Also, curcumol-mediated apoptosis of HSC-T6 were reversed by LY294002 and Bay 11-7082. Taken together, our findings perfectly support the hypothesis and demonstrate that the inhibition of PI3K/NF-κB pathway by curcumol lead to HSC-T6 apoptosis. Thus, our study indicates that curcumol is a potential candidate for further preclinical study aimed at the treatment of liver fibrosis.

A new histone deacetylase inhibitor improves liver fibrosis in BDL rats through suppression of hepatic stellate cells

Background and Purpose

Activation of hepatic stellate cells (HSCs) is a crucial step in the pathogenesis of hepatic fibrosis. Histone deacetylase (HDAC) is an attractive target in liver fibrosis because it plays a key role in gene expression and cell differentiation. We have developed a HDAC inhibitor, N-hydroxy-7-(2-naphthylthio)heptanomide (HNHA), and investigated the anti-fibrotic activity of HNHA in vitro and in vivo.

Experimental Approach

We investigated the anti-fibrotic effect of HNHA on mouse and human HSC activation in vitro and in the liver of bile duct-ligated (BDL) rats in vivo using cell proliferation assays, cell cycle analysis, biochemical assay, immunohistochemistry and Western blots. Liver pathology was assessed with histochemical techniques.

Key Results

HNHA inhibited proliferation and arrested the cell cycle via p21 induction in HSCs. In addition, HNHA induced apoptosis of HSCs, which was correlated with reduced COX-2 expression, NF-κB activation and cell death signals. HNHA restored liver function and decreased the accumulation of extracellular matrix in the liver via suppression of HSC activation in BDL rats in vivo. HNHA administration also increased survival in BDL rats.

Conclusions and Implications

HNHA improved liver function, suppressed liver fibrosis and increased survival of BDL rats, accompanied by reduction of cell growth, activation and survival of HSCs. These findings show that HNHA may be a potent anti-fibrosis agent against hepatic fibrosis because of its multi-targeted inhibition of HSC activity in vivo and in vitro.

Cellular and molecular mechanisms in liver fibrogenesis

Liver fibrogenesis is a dynamic and highly integrated molecular, tissue and cellular process, potentially reversible, that drives the progression of chronic liver diseases (CLD) towards liver cirrhosis and hepatic failure. Hepatic myofibroblasts (MFs), the pro-fibrogenic effector cells, originate mainly from activation of hepatic stellate cells and portal fibroblasts being characterized by a proliferative and survival attitude. MFs also contract in response to vasoactive agents, sustain angiogenesis and recruit and modulate activity of cells of innate or adaptive immunity. Chronic activation of wound healing and oxidative stress as well as derangement of epithelial-mesenchymal interactions are "major" pro-fibrogenic mechanisms, whatever the etiology. However, literature has outlined a complex network of pro-fibrogenic factors and mediators proposed to modulate CLD progression, with some of them being at present highly debated in the field, including the role of epithelial to mesenchymal transition and Hedgehog signaling pathways. Hypoxia and angiogenesis as well as inflammasomes are recently emerged as ubiquitous pro-inflammatory and pro-fibrogenic determinants whereas adipokines are mostly involved in CLD related to metabolic disturbances (metabolic syndrome and/or obesity and type 2 diabetes). Finally, autophagy as well as natural killer and natural killer-T cells have been recently proposed to significantly affect fibrogenic CLD progression.

Serum levels of apoptosis inhibitor of macrophage are associated with hepatic fibrosis in patients with chronic hepatitis C

Background

Apoptosis inhibitor of macrophage (AIM) and adipocytokines are involved in the metabolic syndrome, which has been putatively associated with the progression of chronic hepatitis C (CHC). However, the association between these cytokines and CHC is not fully elucidated. The aim of this study is to test whether serum levels of AIM and adipocytokines are associated with histological features, homeostasis model assessment-insulin resistance index (HOMA-IR), or whole body insulin sensitivity index (WBISI) in CHC patients.

Methods

Serum samples were obtained from 77 patients with biopsy-proven CHC. In 39 patients without overt diabetes mellitus, a 75 g oral glucose tolerance test (OGTT) was performed and HOMA-IR and WBISI were calculated.

Results

A serum AIM level of ≥1.2 μg/ml was independently associated with advanced hepatic fibrosis (F2 or F3) (odds ratio [OR], 5.612; 95% confidence interval [CI], 1.103–28.563; P = 0.038) based on a multivariate analysis, but there was no significant association between AIM and hepatic steatosis or inflammation. Furthermore, a serum leptin level of ≥8.6 ng/ml was independently associated with the presence of hepatic steatosis (≥5%) (OR, 6.195; 95% CI, 1.409–27.240; P = 0.016), but not hepatic fibrosis or inflammation. No relationship was observed between levels of adiponectin or resistin and hepatic histological parameters based on a multivariate analysis. Although serum levels of leptin, resistin, and adiponectin were significantly correlated with HOMA-IR and WBISI, there was no significant relationship between serum AIM levels and HOMA-IR or WBISI, respectively.

Conclusion

High serum levels of AIM in CHC patients are potentially related to advanced hepatic fibrosis. AIM and adipocytokines are possibly associated with pathological changes via a different mechanism.

HS-173, a novel PI3K inhibitor, attenuates the activation of hepatic stellate cells in liver fibrosis

Hepatic stellate cells (HSCs) are the primary source of matrix components in liver disease such as fibrosis. Phosphatidylinositol 3-kinase (PI3K) signaling in HSCs has been shown to induce fibrogenesis. In this study, we evaluated the anti-fibrotic activity of a novel imidazopyridine analogue (HS-173) in human HSCs as well as mouse liver fibrosis. HS-173 strongly suppressed the growth and proliferation of HSCs and induced the arrest at the G2/M phase and apoptosis in HSCs. Furthermore, it reduced the expression of extracellular matrix components such as collagen type I, which was confirmed by an in vivo study. We also observed that HS-173 blocked the PI3K/Akt signaling pathway in vitro and in vivo. Taken together, HS-173 suppressed fibrotic responses such as cell proliferation and collagen synthesis by blocking PI3K/Akt signaling. Therefore, we suggest that this compound may be an effective therapeutic agent for ameliorating liver fibrosis through the inhibition of PI3K signaling.

Apoptosis and angiogenesis: an evolving mechanism for fibrosis

Fibrosis, seen in the liver, lung, heart, kidney, and skin, is a significant global disease burden. Currently, therapeutic treatment is limited, and the number of cases continues to grow. Apoptosis has been identified as a potential initiator and propagator of fibrosis. This review specifically examines the correlation between the presence of apoptotic cells and their effect on fibroblast phenotype and collagen metabolism in several different experimental models of fibrosis. Fibrosis in these models is generally preceded by robust angiogenesis and vascular regression, suggesting that the vascular apoptotic burden may be important to fibrotic outcomes. This review considers the emerging evidence that angiogenesis or vascular regression contributes to fibrosis and identifies initial vascular outgrowth or vascular apoptotic cell presence as possible regulators of fibrosis. A further understanding of the cellular mechanisms of fibrosis may suggest novel methods for the reduction of the fibrotic response and promotion of regeneration.

Cytotoxic effect of amphotericin B in a myofibroblast cell line

In this study we investigate whether Amphotericin B (AmB), a widely used antifungal agent, could decrease the proliferation of a myofibroblast cell line - GRX, a model of activated hepatic stellate cells (HSC). Three different hepatic cell lines (GRX, Hep G2 and ARL-6) were treated with two concentrations of AmB (1.25 μg/mL or 2.50 μg/mL). Cytotoxicity was assessed by MTT assay. The effects of AmB on GRX migration was evaluated by Wound-healing Assay. Cell cycle arrest was investigated by flow cytometry. Apoptosis and autophagy were analyzed by Caspase 3 and LC3 immunostaining, respectively. Treatment with AmB 1.25 or 2.50 μg/mL showed a decrease in viability of GRX cells. This decrease was not observed for Hep G2 or ARL-6 in any of the two AmB concentrations tested. GRX cells treated with 1.25 μg/mL AmB were unable to close the wound after 96 h. Cell cycle analysis showed an increase in sub-G1 population and a decrease in G2/M population in AmB-treated cells. In addition, AmB-treated GRX cells showed increased expression of LC-3 and Caspase-3 by immunohistochemistry, suggesting an increase in both autophagy and apoptosis. Here we show that AmB is cytotoxic for GRX cells, a model of activated HSC, but not for hepatic lineages HepG2 and ARL6.

Absence of Nogo-B (reticulon 4B) facilitates hepatic stellate cell apoptosis and diminishes hepatic fibrosis in mice

Nogo-B (reticulon 4B) accentuates hepatic fibrosis and cirrhosis, but the mechanism remains unclear. The aim of this study was to identify the role of Nogo-B in hepatic stellate cell (HSC) apoptosis in cirrhotic livers. Cirrhosis was generated by carbon tetrachloride inhalation in wild-type (WT) and Nogo-A/B knockout (Nogo-B KO) mice. HSCs were isolated from WT and Nogo-B KO mice and cultured for activation and transformation to myofibroblasts (MF-HSCs). Human hepatic stellate cells (LX2 cells) were used to assess apoptotic responses of activated HSCs after silencing or overexpressing Nogo-B. Livers from cirrhotic Nogo-B KO mice showed significantly reduced fibrosis (P < 0.05) compared with WT mice. Apoptotic cells were more prominent in fibrotic areas of cirrhotic Nogo-B KO livers. Nogo-B KO MF-HSCs showed significantly increased levels of apoptotic markers, cleaved poly (ADP-ribose) polymerase, and caspase-3 and -8 (P < 0.05) compared with WT MF-HSCs in response to staurosporine. Treatment with tunicamycin, an endoplasmic reticulum stress inducer, increased cleaved caspase-3 and -8 levels in Nogo-B KO MF-HSCs compared with WT MF-HSCs (P < 0.01). In LX2 cells, Nogo-B knockdown enhanced apoptosis in response to staurosporine, whereas Nogo-B overexpression inhibited apoptosis. The absence of Nogo-B enhances apoptosis of HSCs in experimental cirrhosis. Selective blockade of Nogo-B in HSCs may represent a potential therapeutic strategy to mitigate liver fibrosis.

Endoplasmic Reticulum stress induces hepatic stellate cell apoptosis and contributes to fibrosis resolution

BACKGROUND

Survival of hepatic stellate cells (HSCs) is a hallmark of liver fibrosis, while the induction of HSC apoptosis may induce recovery. Activated HSC are resistant to many pro-apoptotic stimuli. To this issue, the role of Endoplasmic Reticulum (ER) stress in promoting apoptosis of HSCs and consequently fibrosis resolution is still debated.

AIM

To evaluate the potential ER stress-mediated apoptosis of HSCs and fibrosis resolution

METHODS

HSCs were incubated with the ER stress agonists, tunicamycin or thapsigargin. In vivo, HSC were isolated from normal, bile duct-ligated (BDL) and bile duct-diverted (BDD) rats.

RESULTS

In activated HSC, the specific inhibitor of ER stress-induced apoptosis, calpastatin, is significantly increased vs. quiescent HSCs. Calpain is conversely reduced in activated HSCs. This pattern of protein expression provides HSCs resistance to the ER stress signals of apoptosis (apoptosis-resistant phenotype). However, both tunicamycin and thapsigargin are able to induce apoptosis in HSCs in vitro, completely reversing the calpain/calpastatin pattern expression. Furthermore, in vivo, the fibrosis resolution observed in rat livers subjected to bile duct ligation (BDL) and subsequent bile duct diversion (BDD), leads to fibrosis resolution through a mechanism of HSCs apoptosis, potentially associated with ER stress: in fact, BDD rat liver shows an increased number of apoptotic HSCs associated with reduced calapstatin and increased calpain protein expression, leading to an apoptosis-sensible phenotype.

CONCLUSIONS

ER stress sensitizes HSC to apoptosis both in vitro and in vivo. Thus, ER stress represents a key target to trigger cell death in activated HSC and promotes fibrosis resolution.

High mobility group box 1 activates Toll like receptor 4 signaling in hepatic stellate cells

AIMS

The aim of the present study was to investigate the effect of high mobility group box 1 (HMGB1), a damage pattern molecule that signals the presence of necrosis, on TLR4 signaling in hepatic stellate cells (HSC).

MAIN METHODS

Immortalized mouse HSC lines JS1, JS2, and JS3 that were either TLR4(+/+), TLR4(-/-), or MyD88(-/-) were transfected with NF-κB or AP-1 responsive luciferase reporter plasmids, followed by stimulation with 100 ng/ml lipopolysacchride (the exogenous TLR4 ligand) or 100 ng/ml HMGB1. The activation of NF-κB or AP-1 activities was determined by a dual-luciferase reporter assay system. The cells were also stimulated with LPS or HMGB1 and collected for the determination of chemotactic cytokine MCP-1 mRNA or proteins secretion. In a separate experiment, the cells were co-stimulated with 10 μg/ml TGF-β1 and LPS or HMGB1 and collected for assessment of fibrogenic mRNA and protein expression.

KEY FINDINGS

HMGB1 stimulation markedly up-regulated MCP-1 mRNA expression and protein secretion, and enhanced TGF-β1-stimulated collagen α2(I) and α-SMA expression in JS1 cells. This was associated with enhanced activation of NF-κB and AP-1 responsive luciferase reporters. On the contrary, JS2 and JS3 cells were hyporesponsive to both LPS and HGMB1 stimulation compared to JS1 cells.

SIGNIFICANCE

As an endogenous ligand of TLR4, HMGB1 activates TLR4 signaling in HSCs to enhance their inflammatory phenotype, indicating that TLR4 signaling need not rely solely on gut-derived LPS for activation during liver injury. HMGB1 also has a synergistic effect with TGF-β1 to stimulate fibrogenic protein expression, which is likely to be TLR4 dependent.

The improving effects on hepatic fibrosis of interferon-γ liposomes targeted to hepatic stellate cells

No satisfactory anti-fibrotic therapies have yet been applied clinically. One of the main reasons is the inability to specifically target the responsible cells to produce an available drug concentration and the side-effects. Exploiting the key role of the activated hepatic stellate cells (HSCs) in both hepatic fibrogenesis and over-expression of platelet-derived growth factor receptor- (PDGFR- ), we constructed targeted sterically stable liposomes (SSLs) modified by a cyclic peptide (pPB) with affinity for the PDGFR- to deliver interferon (IFN)- to HSCs. The pPB-SSL-IFN- showed satisfactory size distribution. In vitro pPB-SSL could be taken up by activated HSCs. The study of tissue distribution via living-body animal imaging showed that the pPB-SSL-IFN- mostly accumulated in the liver until 24 h. Furthermore, the pPB-SSL-IFN- showed more significant remission of hepatic fibrosis. In vivo the histological Ishak stage, the semiquantitative score for collagen in fibrotic liver and the serum levels of collagen type IV-C in fibrotic rats treated with pPB-SSL-IFN- were less than those treated with SSL-IFN- , IFN- and the control group. In vitro pPB-SSL-IFN- was also more effective in suppressing activated HSC proliferation and inducing apoptosis of activated HSCs. Thus the data suggest that pPB-SSL-IFN- might be a more effective anti-fibrotic agent and a new opportunity for clinical therapy of hepatic fibrosis.

The role of redox mechanisms in hepatic chronic wound healing and fibrogenesis

Under physiological conditions, intracellular and tissue levels of reactive oxygen species (ROS) are carefully controlled and employed as fine modulators of signal transduction, gene expression and cell functional responses (redox signaling). A significant derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, plays a role in the pathogenesis of human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis, including chronic liver diseases. In this chapter major concepts and mechanisms in redox signaling will be briefly recalled to introduce a number of selected examples of redox-related mechanisms that can actively contribute to critical events in the natural history of a chronic liver diseases, including induction of cell death, perpetuation of chronic inflammatory responses and fibrogenesis. A major focus will be on redox-dependent mechanisms involved in the modulation of phenotypic responses of activated, myofibroblast-like, hepatic stellate cells (HSC/MFs), still considered as the most relevant pro-fibrogenic cells operating in chronic liver diseases.

Synergistic inhibition of hepatocellular carcinoma growth by cotargeting chromatin modifying enzymes and poly (ADP-ribose) polymerases

Hepatocellular carcinoma (HCC) is a particularly lethal form of cancer, yet effective therapeutic options for advanced HCC are limited. The poly(ADP-ribose) polymerases (PARPs) and histone deacetylases (HDACs) are emerging to be among the most promising targets in cancer therapy, and sensitivity to PARP inhibition depends on homologous recombination (HR) deficiency and inhibition of HDAC activity blocks the HR pathway. Here, we tested the hypothesis that cotargeting both enzymatic activities could synergistically inhibit HCC growth and defined the molecular determinants of sensitivity to both enzyme inhibitors. We discovered that HCC cells have differential sensitivity to the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) and PARP inhibitor olaparib, and identified one pair of cell lines, termed SNU-398 and SNU-449, with sensitive versus resistant phenotype to both enzyme inhibitors, respectively. Coadministration of SAHA and olaparib synergistically inhibited the growth of SNU-398 but not SNU-449 cells, which was associated with increased apoptosis and accumulated unrepaired DNA damage. Multiple lines of evidence demonstrate that the hepatic fibrosis/hepatic stellate cell activation may be an important genetic determinant of cellular sensitivity to both enzymatic inhibitors, and coordinate activation or inactivation of the aryl hydrocarbon receptor (AhR) and cyclic adenosine monophosphate (cAMP)-mediated signaling pathways are involved in cell response to SAHA and olaparib treatment.

CONCLUSION

These findings suggest that combination therapy with both enzyme inhibitors may be a strategy for therapy of sensitive HCC cells, and identification of these novel molecular determinants may eventually guide the optimal use of PARP and HDAC inhibitors in the clinic.

Mechanisms and biomarkers of apoptosis in liver disease and fibrosis

Liver fibrosis and cirrhosis are a major cause of morbidity and mortality worldwide. Development of the fibrotic scar is an outcome of chronic liver diseases of varying aetiologies including alcoholic liver disease (ALD) nonalcoholic liver disease (NAFLD) including non-alcoholic steatohepatitis (NASH) viral hepatitis B and C (HBV, HCV). The critical step in the development of scar is activation of hepatic stellate cells (HSCs), which become the primary source of extracellular matrix. Aberrant apoptosis is a feature of chronic liver diseases and is associated with worsening stages of fibrosis. However, apoptosis is also the main mechanism promoting the resolution of fibrosis, and spontaneous or targeted apoptosis of HSC is associated with regression of fibrosis in animal models and patients with chronic liver disease. Given the importance of apoptosis in disease progression and resolution, there is much interest in precisely delineating the mechanisms involved and also developing biomarkers that accurately reflect the underlying pathogenesis. Here, we review the mechanisms driving apoptosis in development of liver disease and use of apoptosis -related biomarkers to aid in clinical diagnosis. Finally, we will also examine the recent literature regarding new insights into mechanisms involved in apoptosis of activated HSCs as possible method of fibrosis regression.

Oxidative Stress and Hepatic Stellate Cells: A PARADOXICAL RELATIONSHIP

In physiology, reactive oxygen species (ROS) are produced by most cells for normal function and as a defense mechanism against foreign particles, microbes and viruses. Hepatic macrophages (Kupffer cells), sinusoidal endothelial cells, hepatocytes and hepatic stellate cells (HSCs) are all capable of generating ROS in physiology and pathology. ROS are also produced by infiltrating inflammatory cells during acute and chronic liver injury. Increased levels of ROS have been implicated in apoptotic/necrotic death of hepatocytes, and liver failure. In contrast to causing injury to hepatocytes, ROS and lipid peroxidation products induce transdifferentiation of the quiescent HSCs into an activated highly proliferative myofibroblast-like phenotype. ROS and lipid peroxidation products also stimulate the synthesis of extracellular matrix (ECM) by activated HSCs. Deposition of excessive amounts of ECM is the primary mechanism of fibrosis and cirrhosis of the liver, and interactions between ROS and HSCs appear to play a major role in this pathology. Although these findings suggest that HSCs are resistant to the injurious actions of ROS, there is compelling evidence demonstrating ROS-induced death of activated HSCs. Detailed mechanistic understanding of such paradoxical interactions between ROS and HSCs will be critical for developing therapies for chronic fibrotic liver disease.

The biphasic nature of hypoxia-induced directional migration of activated human hepatic stellate cells

Liver fibrogenesis is sustained by pro-fibrogenic myofibroblast-like cells (MFs), mainly originating from activated hepatic stellate cells (HSC/MFs) or portal (myo)fibroblasts, and is favoured by hypoxia-dependent angiogenesis. Human HSC/MFs were reported to express vascular-endothelial growth factor (VEGF) and VEGF-receptor type 2 and to migrate under hypoxic conditions. This study was designed to investigate early and delayed signalling mechanisms involved in hypoxia-induced migration of human HSC/MFs. Signal transduction pathways and intracellular generation of reactive oxygen species (ROS) were evaluated by integrating morphological, cell, and molecular biology techniques. Non-oriented and oriented migration were evaluated by using wound healing assay and the modified Boyden's chamber assay, respectively. The data indicate that hypoxia-induced migration of HSC/MFs is a biphasic process characterized by the following sequence of events: (a) an early (15 min) and mitochondria-related increased generation of intracellular ROS which (b) was sufficient to switch on activation of ERK1/2 and JNK1/2 that were responsible for the early phase of oriented migration; (c) a delayed and HIF-1α-dependent increase in VEGF expression (facilitated by ROS) and its progressive, time-dependent release in the extracellular medium that (d) was mainly responsible for sustained migration of HSC/MFs. Finally, immunohistochemistry performed on HCV-related fibrotic/cirrhotic livers revealed HIF-2α and haem-oxygenase-1 positivity in hepatocytes and α-SMA-positive MFs, indicating that MFs were likely to be exposed in vivo to both hypoxia and oxidative stress. In conclusion, hypoxia-induced migration of HSC/MFs involves an early, mitochondrial-dependent ROS-mediated activation of ERK and JNK, followed by a delayed- and HIF-1α-dependent up-regulation and release of VEGF.

Peroxisome proliferator-activated receptor-γ cross-regulation of signaling events implicated in liver fibrogenesis

Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear receptor with transcriptional activity controlling multiple physical and pathological processes. Recently, PPARγ has been implicated in the pathogenesis of liver fibrosis. Its depleted expression has strong associations with the activation and transdifferentiation of hepatic stellate cells, the central event in liver fibrogenesis. Studies over the past decade demonstrate that PPARγ cross-regulates a number of signaling pathways mediated by growth factors and adipokines, and cellular events including apoptosis and senescence. These signaling and cellular events and their molecular interactions with PPARγ system are profoundly involved in liver fibrogenesis. We critically summarize these mechanistic insights into the PPARγ regulation in liver fibrogenesis based on the updated findings in this area. We conclude with a discussion of the impacts of these discoveries on the interpretation of liver fibrogenesis and their potential therapeutic implications. PPARγ activation could be a promising strategy for antifibrotic therapy.

Current status of novel antifibrotic therapies in patients with chronic liver disease

Fibrosis accumulation is a dynamic process resulting from a wound-healing response to acute or chronic liver injury of all causes. The cascade starts with hepatocyte necrosis and apoptosis, which instigate inflammatory signaling by chemokines and cytokines, recruitment of immune cell populations, and activation of fibrogenic cells, culminating in the deposition of extracellular matrix. These key elements, along with pathways of transcriptional and epigenetic regulation, represent fertile therapeutic targets. New therapies include drugs specifically designed as antifibrotics, as well as drugs already available with well-established safety profiles, whose mechanism of action may also be antifibrotic. At the same time, the development of noninvasive fibrogenic markers, and techniques (e.g. fibroscan), as well as combined scoring systems incorporating serum and clinical features will allow improved assessment of therapy response. In aggregate, the advances in the elucidation of the biology of fibrosis, combined with improved technologies for assessment will provide a comprehensive framework for design of antifibrotics and their analysis in well-designed clinical trials. These efforts may ultimately yield success in halting the progression of, or reversing, liver fibrosis.

Inhibition of PDGF, TGF-β, and Abl signaling and reduction of liver fibrosis by the small molecule Bcr-Abl tyrosine kinase antagonist Nilotinib

BACKGROUND & AIMS

Nilotinib is a novel tyrosine kinase inhibitor of Bcr-Abl and other kinases. In this study, we have examined its activity as an anti-fibrotic agent.

METHODS

The in vitro effect of Nilotinib on rat and human HSCs was assessed using proliferation assays and Western blotting. The in vivo antifibrotic efficacy of Nilotinib was assessed in mice with liver fibrosis induced by CCl(4) and bile duct ligation (BDL).

RESULTS

Nilotinib inhibited proliferation, migration, and actin filament formation, as well as the expression of α-SMA and collagen in activated HSCs. Nilotinib induced apoptosis of HSCs, which was correlated with reduced bcl-2 expression, increased p53 expression, cleavage of PARP, as well as increased expression of PPARγ and TRAIL-R. Nilotinib also induced cell cycle arrest, accompanied by increased expression of p27 and downregulation of cyclin D1. Interestingly, Nilotinib not only inhibited activation of PDGFR, but also TGFRII through Src. Nilotinib significantly inhibited PDGF and TGFβ-simulated phosphorylation of ERK and Akt. Furthermore, PDGF- and TGFβ-activated phosphorylated form(s) of Abl in human HSCs were inhibited by Nilotinib. In vivo, Nilotinib reduced collagen deposition and α-SMA expression in CCl(4) and BDL-induced fibrosis. These beneficial effects were associated with suppressed expression of procollagen-(I), TIMP-1, CD31, CD34, VEGF, and VEGFR. Nilotinib could induce HSC undergoing apoptosis in vivo, which was correlated with downregulation of bcl-2. We also observed reduced expression of phosphorylated ERK, Akt, and Abl in the Nilotinib-treated CCl(4) and BDL livers. In addition to its antifibrotic activity, the drug was hepatoprotective and reduced the elevations of ALT and AST after CCl(4) and BDL.

CONCLUSIONS

These studies uncover a novel role of Bcr-Abl activity in treatment of liver fibrosis through multiple mechanisms and indicate that Nilotinib represents a potentially effective antifibrotic agent.

Elevated systemic monocyte chemoattractrant protein-1 in hepatic steatosis without significant hepatic inflammation

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity and the metabolic syndrome. It encompasses a clinico-pathologic spectrum of conditions ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). The latter develops upon pro-inflammatory cell infiltration and is widely considered as the first relevant pathophysiological step in NAFLD-progression. The chemokine monocyte chemoattractant protein 1 (MCP-1) plays an important role in the progression of hepatic inflammation and fibrosis, and both increased hepatic expression and circulating serum levels have been described in NASH. Here, we aimed to investigate MCP-1 expression in simple hepatic steatosis. Upon feeding a high-fat diet mice developed hepatic steatosis in the absence of significant hepatic inflammation, but elevated hepatic MCP-1 expression compared to control mice fed a standard chow. Interestingly, high-fat diet fed mice had significantly higher MCP-1 serum levels, and MCP-1 mRNA expression was significantly increased in visceral adipose tissue. Furthermore, MCP-1 serum levels were also elevated in patients with ultrasound-diagnosed NAFLD and correlated with the body-mass index and fasting glucose. In conclusion, our data indicate both the liver and adipose tissue as cellular sources of elevated circulating MCP-1 levels already in the early phase of hepatic steatosis. Since MCP-1 derived from visceral adipose tissue reaches the liver via portal circulation at high concentrations it may significantly contribute to the progression of simple steatosis to NASH.

S-Nitroso-N-acetylcysteine induces de-differentiation of activated hepatic stellate cells and promotes antifibrotic effects in vitro

Nitric oxide (NO) has been shown to act as a potent antifibrogenic agent by decreasing myofibroblast differentiation. S-Nitroso-N-acetylcysteine (SNAC), a NO donor, attenuates liver fibrosis in rats, but the cellular and molecular mechanisms on liver myofibroblast-like phenotype still remain unknown. Here, we investigate the antifibrotic effects of SNAC on hepatic stellate cells, the major fibrogenic cell type in the liver. A murine GRX cell line was incubated with SNAC (100μM) or vehicle (control group) for 72h. Cell viability was measured by MTT colorimetric assay and the conversion of myofibroblast into quiescent fat-storing cell phenotype was evaluated by Oil-Red-O staining. TGFβ-1, TIMP-1, and MMP-13 levels were measure in the supernatant by ELISA. Profibrogenic- and fibrolytic-related gene expression was quantified using real-time qPCR. SNAC induced phenotype conversion of myofibroblast-like phenotype into quiescent cells. SNAC decreased gene and protein expression of TGFβ-1 and MMP-2 compared to control groups. Besides, SNAC down-regulated profibrogenic molecules and up-regulated MMP-13 gene expression, which plays a key role in the degradation of interstitial collagen in liver fibrosis. In conclusion, these findings demonstrate that SNAC efficiently can modulate the activation and functionality of murine hepatic stellate cells and could be considered as an antifibrotic treatment to human liver fibrosis.

Reversal of hepatic fibrosis: pathophysiological basis of antifibrotic therapies

Chronic liver injuries of different etiologies eventually lead to fibrosis, a scarring process associated with increased and altered deposition of extracellular matrix in the liver. Progression of fibrosis has a major worldwide clinical impact due to the high number of patients affected by chronic liver disease which can lead to severe complications, expensive treatment, a possible need for liver transplantation, and death. Liver fibrogenesis is characterized by activation of hepatic stellate cells and other extracellular matrix producing cells. Liver fibrosis may regress following specific therapeutic interventions. Other than removing agents causing chronic liver damage, no antifibrotic drug is currently available in clinical practice. The extent of liver fibrosis is variable between individuals, even after controlling for exogenous factors. Thus, host genetic factors are considered to play an important role in the process of liver scarring. Until recently it was believed that this process was irreversible. However, emerging experimental and clinical evidence is starting to show that even cirrhosis in its early stages is potentially reversible.

Reversal of hepatic fibrosis: pathophysiological basis of antifibrotic therapies

Chronic liver injuries of different etiologies eventually lead to fibrosis, a scarring process associated with increased and altered deposition of extracellular matrix in the liver. Progression of fibrosis has a major worldwide clinical impact due to the high number of patients affected by chronic liver disease which can lead to severe complications, expensive treatment, a possible need for liver transplantation, and death. Liver fibrogenesis is characterized by activation of hepatic stellate cells and other extracellular matrix producing cells. Liver fibrosis may regress following specific therapeutic interventions. Other than removing agents causing chronic liver damage, no antifibrotic drug is currently available in clinical practice. The extent of liver fibrosis is variable between individuals, even after controlling for exogenous factors. Thus, host genetic factors are considered to play an important role in the process of liver scarring. Until recently it was believed that this process was irreversible. However, emerging experimental and clinical evidence is starting to show that even cirrhosis in its early stages is potentially reversible.

Intracellular reactive oxygen species are required for directional migration of resident and bone marrow-derived hepatic pro-fibrogenic cells

BACKGROUND & AIMS

Liver fibrogenesis is sustained by myofibroblast-like cells originating from hepatic stellate cells (HSC/MFs), portal fibroblasts or bone marrow-derived cells, including mesenchymal stem cells (MSCs). Herein, we investigated the mechanistic role of intracellular generation of reactive oxygen species (ROS) and redox-sensitive signal transduction pathways in mediating chemotaxis, a critical profibrogenic response for human HSC/MFs and for MSC potentially engrafting chronically injured liver.

METHODS

Intracellular generation of ROS and signal transduction pathways were evaluated by integrating morphological and molecular biology techniques. Chemokinesis and chemotaxis were evaluated by wound healing assay and modified Boyden's chamber assay, respectively. Additional in vivo evidence was obtained in human specimens from HCV-related cirrhosis.

RESULTS

Human MSCs and HSC/MFs migrate in response to a panel of polypeptide chemoattractants and extracellularly generated superoxide anion. All polypeptides induced a NADPH-oxidase-dependent intracellular rise in ROS, resulting in activation of ERK1/2 and JNK1/2. Moreover, menadione or 2,3-dimethoxy-1,4-naphthoquinone, which generate intracellular superoxide anion or hydrogen peroxide, respectively, induced ERK1/2 and JNK1/2 activation and migration. JNK1 activation was predominant for migration as shown by specific silencing. Finally, activation of ERK1/2 and JNK1/2 was found in extracts obtained from HSC/MFs during the course of an oxidative stress-mediated model of liver injury and phosphorylated JNK1/2 isoforms were detected in α-smooth muscle actin-positive myofibroblasts lining fibrotic septa in human cirrhotic livers.

CONCLUSIONS

Intracellular generation of ROS, through activation of specific signaling pathways, is a critical event for directional migration of HSC/MFs and MSCs.

Pathogenesis of liver fibrosis

Liver fibrosis is a major cause of morbidity and mortality worldwide due to chronic viral hepatitis and, more recently, from fatty liver disease associated with obesity. Hepatic stellate cell activation represents a critical event in fibrosis because these cells become the primary source of extracellular matrix in liver upon injury. Use of cell-culture and animal models has expanded our understanding of the mechanisms underlying stellate cell activation and has shed new light on genetic regulation, the contribution of immune signaling, and the potential reversibility of the disease. As pathways of fibrogenesis are increasingly clarified, the key challenge will be translating new advances into the development of antifibrotic therapies for patients with chronic liver disease.

Peyronie's disease: perspectives on therapeutic targets

INTRODUCTION

Peyronie's disease (PD) is an acquired benign connective tissue disorder of the penis, characterized by the development of fibrotic plaques, that can cause different degrees of bending, narrowing or shortening. Medical treatment for PD remains a major challenge. Impressive progress in our understanding of the molecular mechanisms of PD pathogenesis has uncovered several promising molecular targets for antifibrotic treatments.

AREAS COVERED

This review covers the literature pertaining to the exploration of therapeutic targets for PD. The search included: i) a MEDLINE search from 1941 to January 2011, limited to English-language medical literature, ii) relevant abstracts from 2009 and 2010, iii) relevant textbooks and iv) a pipeline search for therapeutics in development.

EXPERT OPINION

Rapid translational research depends on our ability to develop rational therapies targeted to penile tunical fibrosis, which necessitate a sound knowledge of the biology, biochemistry and the physiological role of fibroblasts, myofibroblasts and stem cells in PD. Much remains to be learned about the pathogenesis of PD. Although there are many interesting therapeutic targets, we are confronted with some questions when identifying new targets, or when validating potential therapeutic options.

Liver cirrhosis

Liver cirrhosis is a frequent consequence of the long clinical course of all chronic liver diseases and is characterized by tissue fibrosis and the conversion of normal liver architecture into structurally abnormal nodules. Portal hypertension is the earliest and most important consequence of cirrhosis and underlies most of the clinical complications of the disease. Portal hypertension results from an increased intrahepatic resistance combined with increased portal (and hepatic arterial) blood flow. The fibrotic and angio-architectural modifications of liver tissue leading to increased intrahepatic resistance and the degree of portal hypertension seem to be highly correlated until HVPG values of 10-12 mmHg are reached. At this stage, which broadly represents the turning point between 'compensated' and 'decompensated' cirrhosis, additional extra-hepatic factors condition the further worsening of PH. Indeed, a HVPG ≥10-12 mmHg represents a critical threshold beyond which chronic liver disease becomes a systemic disorder with the involvement of other organs and systems. The progressive failure of one of the fundamental functions of the liver, i.e. the detoxification of potentially harmful substances received from the splanchnic circulation and particularly bacterial end-products, is responsible for the establishment of a systemic pro-inflammatory state further accelerating disease progression. The biology of liver cirrhosis is characterized by a constant stimulus for hepatocellular regeneration in a microenvironment characterized by chronic inflammation and tissue fibrosis, thus representing an ideal condition predisposing to the development of hepatocellular carcinoma (HCC). In reason of the significant improvements in the management of the complications of cirrhosis occurred in the past 20 years, HCC is becoming the most common clinical event leading to patient death. Whereas evidence clearly indicates reversibility of fibrosis in pre-cirrhotic disease, the determinants of fibrosis regression in cirrhosis are not sufficiently clear, and the point at which cirrhosis is truly irreversible is not established, either in morphologic or functional terms. Accordingly, the primary end-point of antifibrotic therapy in cirrhotic patients should be the reduction of fibrosis in the context of cirrhosis with a beneficial impact on portal hypertension and the emergence of HCC.

Human primary cultured hepatic stellate cells can be cryopreserved

We compared the morphological and functional characteristics of cultured unfrozen hepatic stellate cells (HSCs) and cryopreserved HSCs obtained from human livers. We used liver tissues obtained by surgical resection from patients with metastatic liver cancer or with hepatocellular carcinoma. HSCs were isolated and allowed to spread in culture. Comparison of morphological and functional features between the unfrozen HSCs and cryopreserved HSCs was performed at each passage using the following techniques: light microscopy, immunohistochemistry, cell growth curve, metallothionein (MTT) assay, and PI staining, Western blot, real-time polymerase chain reaction (PCR), and gene expression analysis using microarrays. The purity of HSCs was more than 90% in all passages. alpha-Smooth muscle actin (SMA-)positive HSCs gradually increased in successive passages, and the positive cell rate and rate of increase in cell number were similar in both groups. Expression of platelet-derived growth factor (PDGF) receptor, transforming growth factor (TGF)-beta receptor, and alpha-SMA mRNAs and protein was similar during each passage in the two groups. Gene expression was nearly identical at each passage in unfrozen and frozen/thawed samples obtained from the same patient. In conclusion, an adequate protocol for the cryopreservation of human primary cultured HSCs could be established.

Hepatic steatosis causes induction of the chemokine RANTES in the absence of significant hepatic inflammation

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum ranging from simple steatosis to cirrhosis. Hepatocellular lipid accumulation is a hallmark of both nonalcoholic steatosis and steatohepatitis (NASH). The latter develops upon pro-inflammatory cell infiltration and is widely considered as the first relevant pathophysiological step in NAFLD-progression. The chemokine CCL5/RANTES plays an important role in the progression of hepatic inflammation and fibrosis. We here aimed to investigate its expression in NAFLD. Incubation of primary human hepatocytes with palmitic acid induced a dose-dependent lipid accumulation, and corresponding dose-dependent RANTES induction in vitro. Furthermore, we observed significantly elevated hepatic RANTES expression in a dietary model of NAFLD, in which mice were fed a high-fat diet for 12 weeks. This diet induced significant hepatic steatosis but only minimal inflammation. In contrast to the liver, RANTES expression was not induced in visceral adipose tissue of the group fed with high-fat diet. Finally, RANTES serum levels were elevated in patients with ultrasound-diagnosed NAFLD. In conclusion, our data indicate hepatocytes as cellular source of elevated hepatic as well as circulating RANTES levels in response to hepatic steatosis. Noteworthy, upregulation of RANTES in response to lipid accumulation occurs in the absence of relevant inflammation, which further indicates that hepatic steatosis per se has pathophysiological relevance and should not be considered as benign.

Update on the pathophysiology of liver fibrosis

Fibrogenesis represents the main pathophysiological consequence of chronic liver disease and leads to life-threatening clinical consequences. The knowledge in this field has grown exponentially in the past 20 years and, currently, evaluation and treatment of liver fibrosis are central issues in hepatology. Classic mechanisms of liver fibrogenesis have been expanded and consolidated over the past few years. Concomitantly, novel mechanisms have been suggested and demonstrated. The aim of this article is to provide an update on these mechanisms with an attempt to integrate classic and novel pathways responsible for the evolution of the fibrogenic process and, potentially, for its regression.

New insights into the antifibrotic effects of sorafenib on hepatic stellate cells and liver fibrosis

BACKGROUND & AIMS

During the process of liver fibrosis, hepatic stellate cells (HSCs) play a critical role in the excessive production of extracellular matrix (ECM). We evaluated the therapeutic effects of sorafenib, a multiple receptor tyrosine kinase inhibitor, targeting platelet-derived growth factor (PDGF) receptor and the Raf/extracellular-signal-regulated kinase (ERK) signaling pathway, on liver fibrosis and HSC proliferation.

METHODS

The in vivo effects of sorafenib were monitored in the livers of rats with liver fibrosis, and simultaneously proliferation assays, apoptosis induction studies, and collagen synthesis measurement were conducted in vitro in rat and human HSCs and primary HSCs.

RESULTS

Sorafenib treatment attenuated liver fibrosis and was associated with a significant decrease in intrahepatic fibrogenesis, hydroxyproline accumulation and collagen deposition. Sorafenib reduced HSC proliferation and resulted in significantly higher levels of apoptosis. Moreover, sorafenib downregulated Cyclin D1 and Cyclin-dependent kinase 4 (Cdk-4), simultaneously increased expression of Fas, Fas-L, and Caspase-3, and decreased the ratio of Bcl-2 to Bax. Sorafenib treatment increased the ratio of matrix metalloproteinases (MMPs) to tissue inhibitor of matrix metalloproteinases (TIMPs) and reduced collagen synthesis in HSCs. Sorafenib inhibited the phosphorylation of ERK, Akt and 70-kDa ribosomal S6 kinase (p70S6K), both in vitro and in vivo.

CONCLUSIONS

Sorafenib induces the suppression of collagen accumulation and HSC growth warranting the use of sorafenib as a potential therapeutic agent in the treatment of liver fibrosis.

Bcl-2 overexpression in hepatic stellate cell line CFSC-2G, induces a pro-fibrotic state

BACKGROUND AND AIM

Development of hepatic fibrosis is a complex process that involves oxidative stress (OS) and an altered balance between pro- and anti-apoptotic molecules. Since Bcl-2 overexpression preserves viability against OS, our objective was to address the effect of Bcl-2 overexpression in the hepatic stellate cells (HSC) cell-line CFSC-2G under acetaldehyde and H(2)O(2) challenge, and explore if it protects these cells against OS, induces replicative senescence and/or modify extracellular matrix (ECM) remodeling potential.

METHODS

To induce Bcl-2 overexpression, HSC cell line CFSC-2G was transfected by lipofection technique. Green fluorescent protein-only CFSC-2G cells were used as a control. Cell survival after H(2)O(2) treatment and total protein oxidation were assessed. To determine cell cycle arrest, proliferation-rate, DNA synthesis and senescence were assessed. Matrix metalloproteinases (MMP), tissue-inhibitor of MMP (TIMP), transglutaminases (TG) and smooth muscle a-actin (alpha-SMA) were evaluated by western blot in response to acetaldehyde treatment as markers of ECM remodeling capacity in addition to transforming growth factor-beta (TGF-beta) mRNA.

RESULTS

Cells overexpressing Bcl-2 survived approximately 20% more than control cells when exposed to H(2)O(2) and approximately 35% proteins were protected from oxidation, but Bcl-2 did not slow proliferation or induced senescence. Bcl-2 overexpression did not change alpha-SMA levels, but it increased TIMP-1 (55%), tissue transglutaminases (tTG) (25%) and TGF-beta mRNA (49%), when exposed to acetaldehyde, while MMP-13 content decreased (47%).

CONCLUSIONS

Bcl-2 overexpression protected HSC against oxidative stress but it did not induce replicative senescence. It increased TIMP-1, tTG and TGF-beta mRNA levels and decreased MMP-13 content, suggesting that Bcl-2 overexpression may play a key role in the progression of fibrosis in chronic liver diseases.

Mediators leading to fibrosis - how to measure and control them in tissue engineering

Fibrosis is the result of an excessive amount of fibrous connective tissue deposited into the extracellular matrix (ECM) space of damaged tissues from injury or disease. Collagens, particularly types I and III are the main constituents of the fibrotic scar tissue as well as a mixture of fibrotic cells. Severely fibrotic tissue will develop chronic healing problems resulting in tissue/organ dysfunction. More attention needs to be given to the fibrotic differentiation and related effects in bioengineered tissues. The current review provides an update on the mechanism behind fibrosis formation as well as technical measurements and preventions.

Rotavirus differentially infects and polyclonally stimulates human B cells depending on their differentiation state and tissue of origin

We have shown previously that rotavirus (RV) can infect murine intestinal B220(+) cells in vivo (M. Fenaux, M. A. Cuadras, N. Feng, M. Jaimes, and H. B. Greenberg, J. Virol. 80:5219-5232, 2006) and human blood B cells in vitro (M. C. Mesa, L. S. Rodriguez, M. A. Franco, and J. Angel, Virology 366:174-184, 2007). However, the effect of RV on B cells, especially those present in the human intestine, the primary site of RV infection, is unknown. Here, we compared the effects of the in vitro RV infection of human circulating (CBC) and intestinal B cells (IBC). RV infected four times more IBC than CBC, and in both types of B cells the viral replication was highly restricted to the memory subset. RV induced cell death in 30 and 3% of infected CBC and IBC, respectively. Moreover, RV induced activation and differentiation into antibody-secreting cells (ASC) of CBC but not IBC when the B cells were present with other mononuclear cells. However, RV did not induce these effects in purified CBC or IBC, suggesting the participation of other cells in activating and differentiating CBC. RV infection was associated with enhanced interleukin-6 (IL-6) production by CBC independent of viral replication. The infection of the anti-B-cell receptor, lipopolysaccharide, or CpG-stimulated CBC reduced the secretion of IL-6 and IL-8 and decreased the number of ASC. These inhibitory effects were associated with an increase in viral replication and cell death and were observed in polyclonally stimulated CBC but not in IBC. Thus, RV differentially interacts with primary human B cells depending on their tissue of origin and differentiation stage, and it affects their capacity to modulate the local and systemic immune responses.

Effects of upregulated expression of microRNA-16 on biological properties of culture-activated hepatic stellate cells

In our previous studies, we identified miR-16 as being downregulated during activation of hepatic stellate cells (HSCs) by microarray hybridization. However, the roles and related mechanisms of miR-16 in HSCs are not understood. In this study, The miRNA RNAi technique was used to analyze the effects of miR-16 on biological properties of HSCs in vitro. The lentiviral vector encoding miR-16 was constructed and transfected. Furthermore, the expression level of miR-16 was measured by real-time PCR. Cellular growth and proliferation capacity were assayed using the cell counting kit-8 (CCK-8). The apoptosis rate and cell-cycle distribution were measured by flow cytometry. Cell morphological characteristics were identified by phase-contrast microscopy, fluorescence microscopy and electron microscopy. The underlying mechanisms related to the changes in biological properties were assessed. The identity of the recombinant plasmid was confirmed by restriction endonuclease analysis and DNA sequencing. Virus titer was 10(8) > ifu/m. Restoring the intracellular miRNAs by miR-16 administration greatly reduced the expression levels of cyclin D1 (CD1). Cell-cycle arrest and typical features of apoptosis were detected in activated HSCs treated with pLV-miR-16. Our results indicate that transduction of miR-16 offers a feasible approach to significantly inhibit HSC proliferation and increase the apoptosis index. Thus, targeted transfer of miR-16 into HSC may be useful for the treatment of hepatic fibrosis.

Effects of IFNα-2a on bcl-2 expression in the fibrotic liver of rats

AIM: To investigate the effects of interferon α-2a (IFNα-2a) on bcl-2 gene expression in the fibrotic liver of rats and explore potential mechanisms involved.

METHODS: Hepatic fibrosis was induced in rats by subcutaneous injection of carbon tetrachloride (CCl₄). Sprague-Dawley rats were randomly divided into normal control group, fibrosis model group and IFNα-2a intervention group. The expression of bcl-2 gene in the liver was detected by reverse transcription-polymerase chain reaction (RT-PCR). Liver tissue samples were taken for conventional hematoxylin and eosin (HE) staining and reticular fiber staining to observe histological changes.

RESULTS: A rat model of liver fibrosis was successfully established. IFNα-2a treatment significantly ameliorated liver fibrosis and fatty degeneration, but showed no impact on hepatic inflammation in fibrotic rats. The expression level of bcl-2 mRNA in the IFNα-2a intervention group was significantly lower than that in the fibrosis model group (P < 0.01), but higher than that in the normal control group (P < 0.01).

CONCLUSION: IFNα-2a can effectively ameliorate CCl₄-induced hepatic fibrosis and liver fatty degeneration possibly via a mechanism associated with downregulating bcl-2 gene expression and controlling apoptosis of HSC.

Lipid accumulation in hepatocytes induces fibrogenic activation of hepatic stellate cells

Despite the initial belief that non-alcoholic fatty liver disease is a benign disorder, it is now recognized that fibrosis progression occurs in a significant number of patients. Furthermore, hepatic steatosis has been identified as a risk factor for the progression of hepatic fibrosis in a wide range of other liver diseases. Here, we established an in vitro model to study the effect of hepatic lipid accumulation on hepatic stellate cells (HSCs), the central mediators of liver fibrogenesis. Primary human hepatocytes were incubated with the saturated fatty acid palmitate to induce intracellular lipid accumulation. Subsequently, human HSCs were incubated with conditioned media (CM) from steatotic or control hepatocytes. Lipid accumulation in hepatocytes induced the release of factors that accelerated the activation and proliferation of HSC, and enhanced their resistance to apoptosis, largely mediated via activation of the PI-3-kinase pathway. Furthermore, CM from steatotic hepatocytes induced the expression of the profibrogenic genes TGF-beta, tissue inhibitor of metallo-proteinase-1 (TIMP-1), TIMP-2 and matrix-metallo-proteinase-2, as well as nuclear-factor kappaB-dependent MCP-1 expression in HSC. In summary, our in vitro data indicate a potential mechanism for the pathophysiological link between hepatic steatosis and fibrogenesis in vivo. Herewith, this study provides an attractive in vitro model to study the molecular mechanisms of steatosis-induced fibrogenesis, and to identify and test novel targets for antifibrotic therapies in fatty liver disease.