Molecular mechanisms of hepatic fibrogenesis

MicroRNA-21/PTEN/Akt axis in the fibrogenesis of biliary atresia

BACKGROUND

MicroRNAs (miRNAs) are short, noncoding RNA molecules that act as post-transcriptional negative regulators of target mRNAs. Increasing evidence suggests that miRNAs are involved in liver fibrotic processes. Biliary atresia (BA) is characterized by rapid and progressive liver fibrosis. Therefore, we investigated the role of miRNA-21in the pathogenesis of BA.

METHODS

We collected liver samples from patients with BA or liver trauma to examine the role of miRNA-21. We examined RNA expression of miRNA-21, phosphatase and tensin homolog deleted on chromosome ten (PTEN), and α-smooth muscle actin (α-SMA) in liver tissue using real-time fluorescence quantitative PCR. Western blot analyses and immunohistochemical staining were performed to evaluate protein expression of PTEN, α-SMA, and phosphorylated AKT in liver.

RESULTS

We found that miRNA-21was upregulated in liver samples from BA patients, whereas PTEN negatively correlated with suppression of the 3'-untranslated region (3'-UTR). Activation of the downstream AKT pathway provoked liver fibrosis by enhancing α-SMA levels.

CONCLUSIONS

The miRNA-21/PTEN/AKT axis promotes the fibrosis process in BA, which might be a potential therapeutic target to improve the prognosis of patients with BA.

Chunggan extract, a traditional herbal formula, ameliorated alcohol-induced hepatic injury in rat model

AIM: To evaluate protective effects of Chunggan extract (CGX), a traditional herbal formula, under 4 wk of alcohol consumption-induced liver injury.

METHODS: Male Sprague-Dawley Rats were orally administered 30% ethanol daily for 4 wk with or without CGX. The pharmaceutical properties were assessed through liver enzymes, histopathology, fibrogenic cytokines, and alcohol metabolism in hepatic tissues as well as by in vitro experiment using HSC-T6 cells.

RESULTS: Four weeks of alcohol consumption notably increased liver enzymes and malondialdehyde levels in serum and hepatic tissue. CGX not only prevented the collagen deposition determined by histopathology and hydroxyproline content, but also normalized transforming growth factor-beta, platelet-derived growth factor-beta and connective tissue growth factor at the gene expression and protein levels in liver tissue. Moreover, CGX treatment also significantly normalized the abnormal changes in gene expression profiles of extracellular matrix proteins, matrix metalloproteinase and their inhibitors, alcohol metabolism, and inflammatory reactions. In the acetaldehyde-stimulated HSC-T6 cells, CGX considerably inhibited collagen production and normalized fibrogenic cytokines in both gene expression and protein levels.

CONCLUSION: The present study evidenced that CGX has hepatoprotective properties via modulation of fibrogenic cytokines and alcohol metabolism in alcoholic liver injury.

Selective α1B- and α1D-adrenoceptor antagonists suppress noradrenaline-induced activation, proliferation and ECM secretion of rat hepatic stellate cells in vitro

AIM

To explore the effects of noradrenaline (NA) on hepatic stellate cells (HSCs) in vitro and to determine the adrenoceptor (AR) subtypes and underlying mechanisms.

METHODS

The distribution and expressions of α1A-, α1B-, and α1D-ARs in HSC-T6 cells were analyzed using immunocytochemistry and RT-PCR. Cell proliferation was evaluated with MTT assay. The expression of HSC activation factors [transforming factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA)], extracellular matrix (ECM) secretion factors [tissue inhibitor of metalloproteinase-1 (TIMP-1) and collagen-Ι (ColΙ)] and PKC-PI3K-AKT signaling components (PKC, PI3K, and AKT) in the cells were detected by Western blotting and RT-PCR.

RESULTS

Both α1B- and α1D-AR were expressed in the membrane of HSC-T6 cells, whereas α1A-AR was not detected. Treatment of the cells with NA concentration-dependently increased cell proliferation (EC50=277 nmol/L), which was suppressed by the α1B-AR antagonist CEC or by the α1D-AR antagonist BMY7378. Furthermore, NA (0.001, 0.1, and 10 μmol/L) concentration-dependently increased the expression of TGF-β1, α-SMA, TIMP-1 and ColΙ, PKC and PI3K, and phosphorylation of AKT in HSC-T6 cells, which were suppressed by CEC or BMY7378, or by pertussis toxin (PT), RO-32-0432 (PKC antagonist), LY294002 (PI3K antagonist) or GSK690693 (AKT antagonist).

CONCLUSION

NA promotes HSC-T6 cell activation, proliferation and secretion of ECM in vitro via activation of Gα-coupled α1B-AR and α1D-AR and the PKC-PI3K-AKT signaling pathway.

Sauchinone attenuates liver fibrosis and hepatic stellate cell activation through TGF-β/Smad signaling pathway

Hepatic stellate cells (HSCs) are key mediators of fibrogenesis, and the regulation of their activation is now viewed as an attractive target for the treatment of liver fibrosis. Here, the authors investigated the ability of sauchinone, an active lignan found in Saururus chinensis, to regulate the activation of HSCs, to prevent liver fibrosis, and to inhibit oxidative stress in vivo and in vitro. Blood biochemistry and histopathology were assessed in CCl4-induced mouse model of liver fibrosis to investigate the effects of sauchinone. In addition, transforming growth factor-β1 (TGF-β1)-activated LX-2 cells (a human HSC line) were used to investigate the in vitro effects of sauchinone. Sauchinone significantly inhibited liver fibrosis, as indicated by decreases in regions of hepatic degeneration, inflammatory cell infiltration, and the intensity of α-smooth muscle actin staining in mice. Sauchinone blocked the TGF-β1-induced phosphorylation of Smad 2/3 and the transcript levels of plasminogen activator inhibitor-1 and matrix metalloproteinase-2 as well as autophagy in HSCs. Furthermore, sauchinone inhibited oxidative stress, as assessed by stainings of 4-hydroxynonenal and nitrotyrosine: these events may have a role in its inhibitory effects on HSCs activation. Sauchinone attenuated CCl4-induced liver fibrosis and TGF-β1-induced HSCs activation, which might be, at least in part, mediated by suppressing autophagy and oxidative stress in HSCs.

Influence of caffeine and hyaluronic acid on collagen biosynthesis in human skin fibroblasts

Aim

The aim of this study was to evaluate the effect of caffeine on collagen biosynthesis in human skin fibroblasts and the influence of hyaluronic acid (HA) on this process.

Materials and methods

Collagen, [³H]-thymidine incorporation, and prolidase activity were measured in confluent human skin fibroblast cultures that had been treated with 1, 2, and 5 mM caffeine and with caffeine and 500 μg/mL HA. Western immunoblot analysis was performed to evaluate expression of β₁-integrin receptor, insulin-like growth factor receptor phospho-Akt protein and mitogen-activated protein kinase (phospho-extracellular signal-regulated kinase).

Results

Caffeine inhibited collagen biosynthesis in a dose-dependent manner. The mechanism of this process was found at the level of prolidase activity. Caffeine significantly inhibited the enzyme activity. The addition of HA had no effect on collagen biosynthesis or prolidase activity in fibroblasts incubated with caffeine. Caffeine also had an inhibitory effect on DNA biosynthesis. HA, however, did not have any significant effect on this process. The inhibition of the expression of β₁-integrin and insulin-like growth factor receptor in fibroblasts incubated with the caffeine indicates a possible mechanism of inhibition of collagen biosynthesis.

Conclusion

Caffeine reduces collagen synthesis in human cultured skin fibroblasts. HA did not have any significant protective effect on this process. This is the first study to our knowledge that reports caffeine-induced inhibition of collagen synthesis in human skin fibroblasts.

Matrix remodeling response of human periodontal tissue cells toward fibrosis upon nicotine exposure

It is widely accepted that fibrosis is frequently observed in the gingiva of smokers. However, the mechanisms by which smoking results in pathological changes in periodontal tissue that lead to fibrosis are not entirely clear. Our former report showed that type I collagen synthesis was promoted by nicotine via CCN family protein 2 in human periodontal tissue cells. Here, we evaluated other aspects of nicotine function from a viewpoint of extracellular matrix (ECM) remodeling. Human gingival fibroblasts (n = 4) and periodontal ligament cells (n = 3) were isolated. The cells were treated with nicotine at a variety of concentrations for 12-48 h. Modulators of matrix remodeling were measured using enzyme-linked immunosorbent assays. Cell migration and morphology were also evaluated. As a result, following treatment with 1 μg/ml nicotine, tissue inhibitor of metalloproteinase-1 and transforming growth factor-β1 production in both cell lysates and supernatants, and matrix metalloproteinases-1 production in cell lysates, were significantly increased (p < 0.05). Compared to controls, cell migration was significantly inhibited (p < 0.005) by nicotine in a time-dependent manner. Electron microscopic analysis revealed the presence of a number of vacuoles in nicotine-treated cells. These results indicate that nicotine not only impairs fibroblast motility, and induces cellular degenerative changes, but also alters ECM-remodeling systems of periodontal cells. Induction of matrix remodeling molecules, combined with type I collagen accumulation, may account for the molecular mechanism of nicotine-induced periodontal fibrosis.

Diethylcarbamazine reduces chronic inflammation and fibrosis in carbon tetrachloride- (CCl₄-) induced liver injury in mice

This study investigated the anti-inflammatory effects of DEC on the CCl₄-induced hepatotoxicity in C57BL/6 mice. Chronic inflammation was induced by i.p. administration of CCl₄ 0.5 μL/g of body weight through two injections a week for 6 weeks. DEC (50 mg/kg) was administered by gavage for 12 days before finishing the CCl₄ induction. Histological analyses of the DEC-treated group exhibited reduced inflammatory process and prevented liver necrosis and fibrosis. Immunohistochemical and immunofluorescence analyses of the DEC-treated group showed reduced COX-2, IL1β, MDA, TGF-β, and αSMA immunopositivity, besides exhibiting decreased IL1β, COX-2, NFκB, IFNγ, and TGFβ expressions in the western blot analysis. The DEC group enhanced significantly the IL-10 expression. The reduction of hepatic injury in the DEC-treated group was confirmed by the COX-2 and iNOS mRNA expression levels. Based on the results of the present study, DEC can be used as a potential anti-inflammatory drug for chronic hepatic inflammation.

Differential protective effects of extra virgin olive oil and corn oil in liver injury: a proteomic study

Extra virgin olive oil (EVOO) presents benefits against chronic liver injury induced by hepatotoxins such as carbon tetrachloride (CCl4); however, the protective mechanisms remain unclear. In the present study, a two-dimensional gel based proteomic approach was constructed to explore the mechanisms. Rats are injected with CCl4 twice a week for 4 weeks to induce liver fibrosis, and were fed laboratory chow plus 20% (w/w) of either corn oil or EVOO over the entire experimental period. Histological staining, MDA assay and fibrogenesis marker gene analysis illustrate that the CCl4-treated animals fed EVOO have a lower fibrosis and lipid peroxidation level in the liver than the corn oil fed group. The proteomic study indicates that the protein expression of thioredoxin domain-containing protein 12, peroxiredoxin-1, thiosulphate sulphurtransferase, calcium-binding protein 1, Annexin A2 and heat shock cognate 71 kDa protein are higher in livers from EVOO-fed rats with the CCl4 treatment compared with those from rats fed with corn oil, whereas the expression of COQ9, cAMP-dependent protein kinase type I-alpha regulatory subunit, phenylalanine hydroxylase and glycerate kinase are lower. Our findings confirmed the benefits of EVOO against chronic liver injury, which may be attributable to the antioxidant effects, hepatocellular function regulation and hepatic metabolism modification effects of EVOO.

Roles of Oxidized Diacylglycerol for Carbon Tetrachloride-induced Liver Injury and Fibrosis in Mouse

Since there is a report that an inhibitor of protein kinase C (PKC) effectively suppresses the development of hepatic fibrosis, it is suggested that the PKC signaling pathway plays an important role in the pathogenesis of hepatic fibrosis. We reported that oxidized diacylglycerol (DAG), which is an activator of PKC, had a remarkably stronger PKC-activating action than un-oxidized DAG. In the present study, we explored the roles of oxidized DAG in hepatic fibrogenesis using mice, the livers of which developed fibrosis by long-term administration of carbon tetrachloride (CCl₄). Liver fibrosis models were created by 4- or 8-week repetitive subcutaneous injections of CCl₄ to the backs of C57BL/6J mice. The amount of oxidized DAG was significantly increased in the CCl₄-treated group. Moreover, it was found that PKCα, βI, βII and δ were activated. In the CCl₄-treated group, phosphorylation of ERK and JNK, which are downstream signal transmitters in the PKC pathway, was increased. It was also found in this group that there was an increase in TIMP-1, which is a fibrogenesis-promoting factor whose expression is enhanced by activated JNK, and of TNF-α, an inflammatory cytokine. Analysis by quantitative real-time RT-PCR showed that expressions of αSMA, collagen I, TNF-α and IL-10 were remarkably increased in the 8-week CCl₄-treated group. The above results strongly suggested that oxidized DAG, which is increased by augmented oxidative stress, activated PKCα, βI, βII and δ molecular species and that these molecular species in turn stimulated the phosphorylation of MAP kinases including ERK and JNK, resulting in enhancement of hepatic fibrogenesis.

Hepatic stellate cell is activated by microRNA-181b via PTEN/Akt pathway

Activation of hepatic stellate cells (HSCs) is an essential event in the initiation and progression of liver fibrosis. MicroRNAs have been shown to play a pivotal role in regulating HSC functions such as cell proliferation, differentiation, and apoptosis. Recently, miR-181b has been reported to promote HSCs proliferation by targeting p27. But whether alpha-smooth muscle actin (α-SMA) or collagens could be promoted by miR-181b in activated HSCs is still not clear. Therefore, the understanding of the role of miR-181b in liver fibrosis remains limited. Our results showed that miR-181b expression was increased much higher than miR-181a expression in vitro in transforming growth factor-β1-induced HSC activation as well as in vivo in carbon tetrachloride-induced rat liver fibrosis. Of note, overexpression of miR-181b significantly increased the expressions level of α-SMA and type I collagen, and further promoted HSCs proliferation. Furthermore, phosphatase and tensin homologs deleted on chromosome 10 (PTEN), a negative regulator of PI3K/Akt pathway, were confirmed as a direct target of miR-181b. We demonstrated that miR-181b could suppress PTEN expression and increase Akt phosphorylation in HSCs. Interestingly, the effects of miR-181b on the activation of HSCs were blocked down by Akt inhibitor LY294002. Our results revealed a profibrotic role of miR-181b in HSC activation and demonstrated that miR-181b could activate HSCs, at least in part, via PTEN/Akt pathway.

Asbestos-associated mesothelial cell autoantibodies promote collagen deposition in vitro

Fibrosis, characterized by excessive collagen protein deposition, is a progressive disease that can fatally inhibit organ function. Prolonged exposure to pathogens or environmental toxicants such as asbestos can lead to chronic inflammatory responses associated with fibrosis. Significant exposure to amphibole asbestos has been reported in and around Libby, Montana due to local mining of asbestos-contaminated vermiculite. These exposures have been implicated in a unique disease etiology characterized predominantly by pleural disorders, including fibrosis. We recently reported the discovery of mesothelial cell autoantibodies (MCAAs) in the sera of Libby residents and demonstrated a positive and significant correlation with pleural disease; however, a mechanistic link was not determined. Here we demonstrate that MCAAs induce pleural mesothelial cells to produce a collagen matrix but do not affect production of the pro-inflammatory cytokine tumor growth factor-β. While autoantibodies commonly induce a pro-fibrotic state by inducing epithelial-mesenchymal transition (EMT) of target cells, we found no evidence supporting EMT in cells exposed to MCAA positive human sera. Although implicated in other models of pulmonary fibrosis, activity of the protein SPARC (secreted protein, acidic and rich in cysteine) did not affect MCAA-induced collagen deposition. However, matrix formation was dependent on matrix metalloproteinase (MMP) activity, and we noted increased expression of MMP-8 and -9 in supernatants of mesothelial cells incubated with MCAA positive sera compared to control. These data suggest a mechanism by which MCAA binding leads to increased collagen deposition through altering MMP expression and provides an important mechanistic link between MCAAs and asbestos-related, autoimmune-induced pleural fibrosis.

GIV/Girdin is a central hub for profibrogenic signalling networks during liver fibrosis

Progressive liver fibrosis is characterized by the deposition of collagen by activated hepatic stellate cells (HSCs). Activation of HSCs is a multiple receptor-driven process in which profibrotic signals are enhanced, and anti-fibrotic pathways are suppressed. Here we report the discovery of a novel signaling platform comprised of G protein subunit, Gαi and GIV, its guanine exchange factor (GEF), which serves as a central hub within the fibrogenic signalling network initiated by diverse classes of receptors. GIV is expressed in the liver after fibrogenic injury and is required for HSC activation. Once expressed, GIV enhances the profibrotic (PI3K-Akt-FoxO1 and TGFβ-SMAD) and inhibits the anti-fibrotic (cAMP-PKA-pCREB) pathways to skew the signalling network in favor of fibrosis, all via activation of Gαi. We also provide evidence that GIV may serve as a biomarker for progression of fibrosis after liver injury and a therapeutic target for arresting and/or reversing HSC activation during liver fibrosis.

Protein O glycosylation regulates activation of hepatic stellate cells

It was reported that O glycosylation is associated with hepatic stellate cell activation and regulates collagen expression. In this study, we aimed to investigate the effect of O glycosylation on the activation of human hepatic stellate cells. We found that the inhibitor of O glycosylation, benzyl-α-GalNAc (2 and 4 mM), could significantly inhibit cells proliferation in a dose-dependent manner. Moreover, benzyl-α-GalNAc decreased the expressions of α-smooth muscle actin, collagen I, and collagen III. The results indicate that O glycosylation is involved in the activation of hepatic stellate cells.

Endoplasmic reticulum stress-induced hepatic stellate cell apoptosis through calcium-mediated JNK/P38 MAPK and Calpain/Caspase-12 pathways

Recent reports considered that it was the disturbance of calcium homeostasis and the accumulation of misfolded proteins in the endoplasmic reticulum (ER) that activated hepatic stellate cells (HSCs) apoptosis and promoted fibrosis resolution. However, the signal-transducing events that are activated by ER stress after HSCs activation were incompletely understood. In this study, we induced ER stress with thapsigargin (TG), and determined the activation of calpain and the cleavage of caspase by analyzing the protein levels and the correspondingly increased intracellular calcium levels and the induction of the proapoptotic transcription factor CHOP. Moreover, the phosphorylation of JNK and p38 MAPK were followed by the activation of the executioner caspases, caspase-3. As expected, preventing an increase in intracellular calcium levels using intracellular calcium chelators, EGTA, and BAPTA/AM, could substantially inhibit the phosphorylation of JNK and p38 MAPK, abolish the activation of calpains, namely caspase-12, caspase-9, and caspase-3, and provide significant protection for TG-treated activated HSCs. Interestingly, pretreatment with p38 MAPK inhibitor SB202190, JNK inhibitor SP600125, the pan-caspase inhibitor z-VAD-FMK, or calpain inhibitors calpeptin, significantly reduced the cell apoptosis and the cleavage of caspase-12 and caspase-3. However, pretreatment with z-VAD-FMK failed to reduce the activation of calpain. Additionally, pretreatment with SB202190 and SP600125 also decreased the expression of CHOP. Importantly, PDGF-induced collagen Col1α1 and α-smooth muscle actin (α-SMA), markers for the perpetuation phase of HSCs activation, were inhibited in TG-treated activated HSCs. These findings showed that the Calpain/Caspase-12 activation induced by ER stress and the JNK/p38 MAPK phosphorylation induced by the increase of intracellular calcium concentration releasing from ER are the novel signaling pathway underlying the molecular mechanism of fibrosis recovery.

Molecular mechanism and treatment of viral hepatitis-related liver fibrosis

Hepatic fibrosis is a wound-healing response to various chronic stimuli, including viral hepatitis B or C infection. Activated myofibroblasts, predominantly derived from the hepatic stellate cells (HSCs), regulate the balance between matrix metalloproteinases and their tissue inhibitors to maintain extracellular matrix homeostasis. Transforming growth factor-β and platelet-derived growth factor are classic profibrogenic signals that activate HSC proliferation. In addition, proinflammatory cytokines and chemokines coordinate macrophages, T cells, NK/NKT cells, and liver sinusoidal endothelial cells in complex fibrogenic and regression processes. In addition, fibrogenesis involves angiogenesis, metabolic reprogramming, autophagy, microRNA, and epigenetic regulations. Hepatic inflammation is the driving force behind liver fibrosis; however, host single nucleotide polymorphisms and viral factors, including the genotype, viral load, viral mutation, and viral proteins, have been associated with fibrosis progression. Eliminating the underlying etiology is the most crucial antifibrotic therapy. Growing evidence has indicated that persistent viral suppression with antiviral therapy can result in fibrosis regression, reduced liver disease progression, decreased hepatocellular carcinoma, and improved chances of survival. Preclinical studies and clinical trials are currently examining several investigational agents that target key fibrogenic pathways; the results are promising and shed light on this debilitating illness.

Synthetic RGDS peptide attenuated lipopolysaccharide/D-galactosamine-induced fulminant hepatic failure in mice

BACKGROUND AND AIM

Fulminant hepatic failure (FHF) is a serious clinic syndrome with extremely poor prognosis and no effective treatment except for liver transplantation. Synthetic RGDS peptide, an inhibitor of integrins, was proved to suppress integrin signals. In this study, we investigated the protection effects of RGDS peptide on lipopolysaccharide/D-galactosamine (LPS/D-GalN)-induced FHF and the underlying molecular mechanisms.

METHODS

Synthetic RGDS peptide was given intraperitoneally 30 min before LPS/D-GalN injection. Liver function and the extent of liver injury were analyzed biochemically and pathologically respectively. Enzyme-linked immunosorbent assay, real-time polymerase chain reaction and Western blotting were used to detect effectors and signaling molecules.

RESULTS

Pretreatment with synthetic RGDS peptide significantly improved LPS/D-GalN-induced mortality, and liver injury as determined by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, as well as pathological analysis. In addition, RGDS peptide significantly reduced tumor necrosis factor (TNF)-α and macrophage inflammatory protein (MIP)-2 production, and decreased myeloperoxidase (MPO) and NF-κB activity. Furthermore, Western blotting indicated that the levels of phospho-integrin β3, phospho-focal adhesion kinase (FAK) and phospho-p38 mitogen-activated protein kinases (MAPK) decreased with RGDS peptide pretreatment.

CONCLUSION

Together, these data suggest that synthetic RGDS peptide protect against LPS/D-GalN-induced FHF by inhibiting inflammatory cells migration and blocking the integrin αVβ3-FAK-p38 MAPK and NF-κB signaling.

Endostar, a novel human recombinant endostatin, attenuates liver fibrosis in CCl4-induced mice

Decreasing hepatic fibrosis remains one of the major therapeutic challenges in hepatology. The present study aims to evaluate the effect of Endostar on both CCl4-induced liver fibrosis in mice and a hepatic stellate cell (HSC) line. Two main models were studied: (i) a liver fibrosis model was induced in BALB/c mice using CCl4 by intraperitoneal injection for six weeks. Six animal groups were studied: group 1: normal animals; group 2: CCl4-induced liver fibrosis; group 3: CCl4 + Endostar 20 mg/kg/d, six weeks; group 4: CCl4 + Endostar 10 mg/kg/d, six weeks; group 5: CCl4 + Endostar 20 mg/kg/d, four weeks; group 6: CCl4 + Endostar 10 mg/kg/d, four weeks corresponded to different Endostar doses and duration of administration. Liver fibrosis was evaluated by histopathological staining and liver hydroxyproline content. Expressions of collagen type I, α-smooth muscle actin ( α-SMA), TGF-β1 and VEGFR were measured by real-time polymerase chain reaction (PCR). (ii) A liver cell model. HSC-T6 cells were cultured with or without Endostar for 12 h or 24 h. Expressions of collagen type I, α-SMA, and TGF-β1 were measured by real-time PCR. Collagen I and transforming growth factor β1 (TGF-β1) contents in cell supernatant were measured by enzyme-linked immunosorbent assay. As compared to the group without Endostar, liver fibrosis scores and hydroxyproline content were decreased in both Endostar groups ( P < 0.05). Moreover, Endostar inhibited the hepatic expression of α-SMA, TGF-β1, Collagen-1, VEGFR1, and VEGFR2 mRNA ( P < 0.05). In the HSC-T6 cell line model, Endostar profoundly inhibited the expression of α-SMA, Collagen-1, and TGF-β1 mRNA. Expressions of Collagen-1 and TGF-β1 protein were decreased in the Endostar group as compared to the normal controls in the supernatant of HSC-T6 cells ( P < 0.05). Endostar decreased both liver fibrosis in CCl4-induced mice and collagen synthesis in HSCs in vitro. Therefore, this recombinant human endostatin is a promising compound for counteracting liver fibrosis.

Expression of Septin4 in human hepatic stellate cells LX-2 stimulated by LPS

Septin4, a member of polymerizing GTP-binding proteins family, is reported to be involved in cytoskeletal organization in mitosis, apoptosis, fibrosis, and other cellular processes. Since various Septin4 expression patterns were reported in different diseases, this study aimed to investigate Septin4 expression in human LX-2 cell line stimulated by lipopolysaccharides (LPS) and attempted to clarify the relationship between Septin4 and hepatic inflammatory injury and fibrosis. In this subject, human stellate cell line LX-2 was stimulated by LPS. The expression of Septin4 was analyzed by Western blot and quantitative real-time PCR. To observe the relationship among Toll-like receptor 4 (TLR4), TGF-β, and Septin4, proteins from the anti-TLR4 antibody blocked cells, as well as the TGF-β-induced cells, were analyzed by the method of Western blot. As the results, LPS could induce the alteration of α-smooth muscle actin and Septin4 expression in LX-2 cells. Septin4 expression was regulated by LPS stimulation through TLR4 and TGF-β pathway. These results therefore suggest that Septin4 may be involved in the process of activation of hepatic stellate cells by LPS stimulation. Further work would focus on the function of Septin4 in hepatic inflammatory injury and fibrosis.

Role of platelets in chronic liver disease and acute liver injury

Platelets contain not only hemostatic factors but also many growth factors that play important roles in wound healing and tissue repair. Platelets have already been used for the promotion of tissue regeneration in the clinical setting, such as dental implantation and plastic surgery. Thrombocytopenia, which is frequently found in patients with chronic liver disease and cirrhosis, is due to various causes such as decreased thrombopoietin production and accelerated platelet destruction caused by hypersplenism. However, the relationship between thrombocytopenia and hepatic pathogenesis and the role of platelets in chronic liver disease are poorly understood. In acute liver injury, it is reported that platelets are recruited to the liver and contribute to liver damage by promoting the induction of chemotactic factors and the accumulation of leukocytes in the liver, whereas platelets or mediators released by platelets can have a protective effect against liver injury. In this review, we highlight the recent accumulated knowledge concerning the role of platelets in chronic liver disease and acute liver injury.

Fluorofenidone attenuates hepatic fibrosis by suppressing the proliferation and activation of hepatic stellate cells

Fluorofenidone (AKF-PD) is a novel pyridone agent. The purpose of this study is to investigate the inhibitory effects of AKF-PD on liver fibrosis in rats and the involved molecular mechanism related to hepatic stellate cells (HSCs). Rats treated with dimethylnitrosamine or CCl4 were randomly divided into normal, model, AKF-PD treatment, and pirfenidone (PFD) treatment groups. The isolated primary rat HSCs were treated with AKF-PD and PFD respectively. Cell proliferation and cell cycle distribution were analyzed by bromodeoxyuridine and flow cytometry, respectively. The expression of collagen I and α-smooth muscle actin (α-SMA) were determined by Western blot, immunohistochemical staining, and real-time RT-PCR. The expression of cyclin D1, cyclin E, and p27(kip1) and phosphorylation of MEK, ERK, Akt, and 70-kDa ribosomal S6 kinase (p70S6K) were detected by Western blot. AKF-PD significantly inhibited PDGF-BB-induced HSC proliferation and activation by attenuating the expression of collagen I and α-SMA, causing G0/G1 phase cell cycle arrest, reducing expression of cyclin D1 and cyclin E, and promoting expression of p27(kip1). AKF-PD also downregulated PDGF-BB-induced MEK, ERK, Akt, and p70S6K phosphorylation in HSCs. In rat liver fibrosis, AKF-PD alleviated hepatic fibrosis by decreasing necroinflammatory score and semiquantitative score, and reducing expression of collagen I and α-SMA. AKF-PD attenuated the progression of hepatic fibrosis by suppressing HSCs proliferation and activation via the ERK/MAPK and PI3K/Akt signaling pathways. AKF-PD may be used as a potential novel therapeutic agent against liver fibrosis.

Up-regulation of miR-200b in biliary atresia patients accelerates proliferation and migration of hepatic stallate cells by activating PI3K/Akt signaling

An increasing body of evidence suggests that miRNAs are involved in fibrotic process of several organs including heart, lung and kidney. It has been observed recently that aberrant expression of miR-200s are associated with hepatic fibrosis. However, the role and underlying mechanism of miR-200s in hepatic fibrogenesis remains unknown. Here, we investigate the role of miR-200b in the activation of immortalized human hepatic stallate cells (HSCs), LX-2 cells. We firstly found that miR-200b significantly enhanced proliferation and migration of LX-2 cells. Secondly, our findings showed that miR-200b enhanced the phosphorylation of Akt, a downstream effector of phosphatidyl-inositol 3-Kinase (PI3K). FOG2, as the targets of fly miR-8 and human miR-200s, directly binds to p85α and inhibits the activation of the PI3K/Akt pathway. Here, we showed that FOG2 protein levels in LX-2 cells were suppressed significantly by miR-200b mimics. FOG2 knockdown by siRNAs activated the PI3K/Akt signaling, which increased cell growth and migration that mimicked the effect of miR-200b. Conversely, LY294002, a highly selective inhibitor of PI3K, could block phosphorylation of Akt and effect of miR-200b. In addition, we showed that miR-200b enhanced the expression of matrix metalloproteinase-2 (MMP-2), which may increase the migration of LX-2 cells. Finally, our results indicated that the expression of miR-200b was unregulated in the biliary atresia (BA) and associated with liver fibrotic progression. These data suggest a potential mechanism for Akt activation through FOG2 down-regulation by miR-200b that can lead to HSC growth and migration. In view of the putative pathogenic role of miR-200b in HSCs, miR-200b may constitute a potential marker for HSC activation and liver fibrosis progression.

Signaling pathways involved in isoprostane-mediated fibrogenic effects in rat hepatic stellate cells

Despite evidence supporting a potential role for F2-isoprostanes (F2-IsoP's) in liver fibrosis, their signaling mechanisms are poorly understood. We have previously provided evidence that F2-IsoP's stimulate hepatic stellate cell (HSC) proliferation and collagen hyperproduction by activation of a modified form of isoprostane receptor homologous to the classic thromboxane receptor (TP). In this paper, we examined which signal transduction pathways are set into motion by F2-IsoP's to exert their fibrogenic effects. HSCs were isolated from rat liver, cultured to their activated myofibroblast-like phenotype, and then treated with the isoprostane 15-F2t-isoprostane (15-F2t-IsoP). Inositol trisphosphate (IP3) and adenosine 3',5'-cyclic monophosphate (cAMP) levels were determined using commercial kits. Mitogen-activated protein kinase (MAPK) and cyclin D1 expression was assessed by Western blotting. Cell proliferation and collagen synthesis were determined by measuring [(3)H]thymidine and [(3)H]proline incorporation, respectively. 15-F2t-IsoP elicited an activation of extracellular-signal-regulated kinase (ERK), p38 MAPK, and c-Jun NH2-terminal kinase (JNK), which are known to be also regulated by G-protein-coupled receptors. Preincubation with specific ERK (PD98059), p38 (SB203580), or JNK (SP600125) inhibitors prevented 15-F2t-IsoP-induced cell proliferation and collagen synthesis. 15-F2t-IsoP decreased cAMP levels within 30 min, suggesting binding to the TPβ isoform and activation of Giα protein. Also, 15-F2t-IsoP increased IP3 levels within a few minutes, suggesting that the Gq protein pathway is also involved. In conclusion, the fibrogenic effects of F2-IsoP's in HSCs are mediated by downstream activation of MAPKs, through TP binding that couples via both Gqα and Giα proteins. Targeting TP receptor, or its downstream pathways, may contribute to preventing oxidative damage in liver fibrosis.

Platelet therapy: A novel strategy for liver regeneration, anti-fibrosis, and anti-apoptosis

Platelets contain bio-physiological substances, including insulin-like growth factor-1, vascular endothelial growth factor, platelet-derived growth factor, hepatocyte growth factor, serotonin, transforming growth factor-β, adenosine diphosphate, adenosine tri-phosphate, and epidermal growth factor. Platelets have conventionally been considered to exacerbate the inflammatory response and liver injury. Recently, platelets were discovered to have a positive impact on the liver. In this review, we present experimental and clinical evidence indicating that platelets accelerate liver regeneration and have anti-fibrosis and anti-apoptosis activity, and we detail the mechanisms of action. Platelets accelerate liver regeneration by three different mechanisms: (1) a direct effect on hepatocytes, (2) a cooperative effect with liver sinusoidal endothelial cells, and (3) a collaborative effect with Kupffer cells. Platelets exert anti-fibrotic activity by deactivating hepatic stellate cells via the adenosine-cyclic adenosine 5’-monophosphate signaling pathway. Platelets prevent hepatocyte apoptosis by activating the Akt pathway and up-regulating Bcl-xL, which suppresses caspase-3 activation. Platelet therapy with thrombopoietin, thrombopoietin receptor agonists, and platelet transfusion has the advantages of convenience and cost-efficiency over other treatments. We propose that in the future, platelet therapy will play a promising role in the treatment of the various liver disorders that currently challenge the surgical field, such as liver failure after a massive hepatectomy, hepatectomy of a cirrhotic liver, and small grafts in liver transplantation.

Profibrotic effect of miR-33a with Akt activation in hepatic stellate cells

MicroRNAs (miRNAs) attract more attention in the pathophysiology of liver fibrosis and miR-33a has been previously demonstrated as involved in the regulation of cholesterol and lipid metabolism. Transforming growth factor-beta1 (TGF-β1) is generally accepted to be the main stimulating factor in the hepatic stellate cells (HSCs) activation, which plays an important role in hepatic fibrosis. However, the involvement and underlying mechanism of miR-33a and its role in TGF-β1-induced hepatic fibrogenesis remains unknown. Here, we investigate the role of miR-33a in the activation of immortalized human HSCs, Lx-2 cells. Our findings have shown that the expression of miR-33a with its host gene sterol regulatory element-binding protein 2 (SREBP2) was more highly expressed in activation of Lx-2 cells than in quiescent cells. The expression of miR-33a on TGF-β1-induced HSCs activation may be modulated via the activation of PI3K/Akt pathway. In addition, miR-33a significantly correlated with TGF-β1-induced expression of α1 (I) collagen (Col1A1) and α-SMA in HSCs. Bioinformatics analyses predict that peroxisome proliferator activated receptor-alpha (PPAR-α) is the potential target of miR-33a. We further found that anti-miR-33a significantly increases target gene PPAR-α mRNA and protein level, suggesting that miR-33a involved in HSCs function might be modulated by targeting PPAR-α. Finally, our results indicate that the expression of miR-33a increased with the progression of liver fibrosis. These results suggested that anti-miR-33a inhibit activation and extracellular matrix production, at least in part, via the activation of PI3K/Akt pathway and PPAR-α and anti sense of miR-33a may be a novel potential therapeutic approach for treating hepatic fibrosis in the future.

Mechanism of interleukin-1β-induced proliferation in rat hepatic stellate cells from different levels of signal transduction

Hepatic stellate cells (HSCs) are the major producers of collagen in the liver. Their conversion from resting cells to proliferative, contractile, and activated cells is a critical step leading to liver fibrosis that is characterized by the deposition of excessive extracellular matrix. Interleukin-1 (IL-1) may play a role in maintaining HSC in a proliferative state that is responsible for hepatic fibrogenesis. The aim of this study was to study the roles of the IL-1 type I receptor (IL-1R1), c-Jun N-terminal kinase (JNK), and activation protein-1 (AP-1) in IL-1β-mediated proliferation in rat HSCs. We showed that IL-1β can upregulate proliferation in rat HSCs; however, inhibition of the JNK pathway could inhibit HSCs proliferation. Furthermore, IL-1β activated IL-1R1 expression, the JNK signaling pathway, and AP-1 activity in a time-dependent manner in rat HSCs. These data demonstrate that IL-1β could promote the proliferation of rat HSCs and that the IL-1R1, JNK, and AP-1 pathways were involved in this process. In summary, IL-1β-induced proliferation is possibly mediated by the IL-1R1, JNK, and AP-1 pathways in rat HSCs. Therefore, drugs that block these pathways may inhibit the proliferation of HSCs and suppress liver fibrosis.

Human platelets inhibit liver fibrosis in severe combined immunodeficiency mice

AIM: To investigate the role of human platelets in liver fibrosis.

METHODS: Severe combined immunodeficiency (SCID) mice were administered CCl₄ and either phosphate-buffered saline (PBS group) or human platelet transfusions (hPLT group). Concentrations of hepatocyte growth factor (HGF), matrix metallopeptidases (MMP)-9, and transforming growth factor-β (TGF-β) in the liver tissue were compared between the PBS and the hPLT groups by enzyme-linked immunosorbent assay (ELISA) and Western blotting. The effects of a human platelet transfusion on liver fibrosis included the fibrotic area, hydroxyproline content, and α-smooth muscle actin (α-SMA) expression, which were evaluated by picrosirius red staining, ELISA, and immunohistochemical staining using an anti-mouse α-SMA antibody, respectively. Phosphorylations of mesenchymal-epithelial transition factor (Met) and SMAD3, downstream signals of HGF and TGF-β, were compared between the two groups by Western blotting and were quantified using densitometry. Hepatocyte apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling. Furthermore, the accumulation of human platelets in the liver 2 h after platelet transfusion was compared between normal and fibrotic livers by immunohistochemical staining using an anti-human CD41 antibody.

RESULTS: The fibrotic area and hydroxyproline content in the liver were both significantly lower in the hPLT group when compared to the PBS group (fibrotic area, 1.7% ± 0.6% vs 2.5% ± 0.6%, P = 0.03; hydroxyproline content, 121 ± 26 ng/g liver vs 156 ± 47 ng/g liver, P = 0.04). There was less α-smooth muscle actin staining in the hPLT group than in the PBS group (0.5% ± 0.1% vs 0.8% ± 0.3%, P = 0.02). Hepatic expression levels of mouse HGF and MMP-9 were significantly higher in the hPLT group than in the PBS group (HGF, 109 ± 13 ng/g liver vs 88 ± 22 ng/g liver, P = 0.03; MMP-9, 113% ± 7%/GAPDH vs 92% ± 11%/GAPDH, P = 0.04). In contrast, the concentration of mouse TGF-β in the liver tissue was significantly lower in the hPLT group than in the PBS group (22 ± 5 ng/g liver vs 39 ± 6 ng/g liver, P = 0.02). Phosphorylation of Met was more prevalent in the hPLT group than in the PBS group (37% ± 4%/GAPDH vs 20% ± 8%/GAPDH, P = 0.03). Phosphorylation of SMAD3 was weaker in the hPLT group than in the PBS group (60% ± 12%/GAPDH vs 84% ± 12%/GAPDH, P = 0.1), although this difference was not significant. Furthermore, a lower rate of hepatocyte apoptosis was observed in the hPLT group than in the PBS group (5.9% ± 1.7% vs 2.9% ± 2.1%, P = 0.02). Significant human platelet accumulation was observed in the fibrotic liver tissues, whereas few platelets accumulated in the normal liver.

CONCLUSION: Human platelets inhibit liver fibrosis in SCID mice. Increased concentration of HGF in the liver suppresses hepatic stellate cell activation, induces MMPs, and inhibits hepatocyte apoptosis.

Effects of Fufang Biejia Ruangan Pills on hepatic fibrosis in vivo and in vitro

AIM: To explore the protective effect and the relevant mechanisms of Fufang Biejia Ruangan Pills (FFBJRGP) on hepatic fibrosis in vivo and in vitro.

METHODS: Hepatic fibrosis was induced by carbon tetrachloride composite factors. Adult Wistar rats were randomly divided into four groups: normal control group; hepatic fibrosis model group; FFBJRGP-treated group at a daily dose of 0.55 g/kg; and colchicine-treated group at a daily dose of 0.1 g/kg. The effects of FFBJRGP on liver function, serum levels of hyaluronic acid (HA), type IV collagen (CIV), type III procollagen (PC III), laminin (LN), histopathology, and expression of transforming growth factor (TGF-β1) and Smad3 in hepatic fibrosis were evaluated in vivo. The effects of FFBJRGP on survival rate, hydroxyproline content and cell cycle distribution were further detected in vitro.

RESULTS: Compared with the hepatic fibrosis model group, rats treated with FFBJRGP showed a reduction in hepatic collagen deposition and improvement in hepatic lesions. Compared with those of the model group, the activities of alanine aminotransferase (62.0 ± 23.7 U/L) and aspartate aminotransferase (98.8 ± 40.0 U/L) in the FFBJRGP-treated group were decreased (50.02 ± 3.7 U/L and 57.2 ± 30.0 U/L, respectively, P < 0.01). Compared with those in the model group, the levels of PCIII (35.73 ± 17.90 μg/mL), HA (563.82 ± 335.54 ng/mL), LN (89.57 ± 7.59 ng/mL) and CIV (29.20 ± 6.17 ng/mL) were decreased to 30.18 ± 9.41, 456.18 ± 410.83, 85.46 ± 7.51 and 28.02 ± 9.45 ng/mL, respectively. Reverse-transcriptase polymerase chain reaction and Western blotting also revealed that expression of TGF-β1 and Smad3 were down-regulated in vivo. Cell proliferation was inhibited, the level of hydroxyproline was decreased compared with the control group (P < 0.01), and the cell cycle was redistributed when exposed to FFBJRGP in vitro.

CONCLUSION: FFBJRGP inhibits hepatic fibrosis in vivo and in vitro, which is probably associated with downregulation of fibrogenic signal transduction of the TGF-β-Smad pathway.

Cyclin-dependent kinases, control of cell cycle and hepatic fibrosis

Multiple etiologies of liver disease lead to liver fibrosis by driving the activation of hepatic stellate cells (HSCs) into a myofibroblast-like phenotype that is contractile, proliferative and fibrogenic. Liver fibrosis is associated with the proliferation of HSCs, and the cell cycle of activated HSCs is abnormal. Cyclin-dependent kinases (CDKs) play essential roles in cell proliferation. However, the molecular mechanisms responsible for the abnormal proliferation of activated HSCs during hepatic fibrogenesis remain to be defined. Here we will review recent progress in understanding the associations among CDKs, the control of cell cycle and hepatic fibrosis, with an aim to reveal the potential mechanisms of hepatic fibrosis.

Recombinant human histidine triad nucleotide-binding protein 1 attenuates liver fibrosis induced by carbon tetrachloride in rats

It is currently thought that the transforming growth factor-β (TGF-β)/Smad signaling pathway acts as a central pathway leading to liver fibrosis, and that the aberrant Wnt/β-catenin signaling pathway also plays a vital role in the development of liver fibrosis. There is evidence that the histidine triad nucleotide-binding protein 1 (Hint1) was capable of inhibiting these two pathways. However, little data regarding the effects of Hint1 on liver fibrosis exists. Thus, we sought to investigate whether the recombinant human Hint1 protein (rhHint1) was capable of attenuating liver fibrosis induced by carbon tetrachloride (CCl4) in rats and the possible underlying mechanism(s) of action. In the present study, purified rhHint1 was obtained using genetic engineering technology. Liver fibrosis was induced in male Sprague-Dawley (SD) rats by the subcutaneous injection of CCl4. The rats were randomly divided into the normal control, the liver fibrosis model and the rhHint1 (doses, 50 and 100 µg/kg)‑treated groups. Following four weeks of treatment, the rhHint1-treated rats exhibited significantly reduced liver fibrosis upon histopathological analysis and lower levels of hydroxyproline. Furthermore, rhHint1 inhibited the expression of α-smooth muscle actin (α-SMA) in the liver tissues. Additionally, rhHint1 lowered the gene expression levels of TGF-β1/Smad3 and β-catenin/cyclin D1, whereas it increased the gene expression levels of Smad7. In conclusion, the results of this study indicated that rhHint1 is capable of attenuating CCl4-induced liver fibrosis by simultaneously targeting multiple pathogenic pathways, which may be developed as a new treatment for liver fibrosis.

Wedelolactone exhibits anti-fibrotic effects on human hepatic stellate cell line LX-2

Wedelolactone is a major coumarin of Eclipta prostrata, which is used for preventing liver damage. However the effects of wedelolactone on hepatic fibrosis remained unexplored. The purpose of this study was to demonstrate the anti-fibrotic effects of wedelolactone on activated human hepatic stellate cell (HSC) line LX-2 and the possible underlying mechanisms by means of MTT assay, Hoechst staining, as well as real-time quantitative PCR and western blot. The results showed that wedelolactone reduced the cellular viability of LX-2 in a time and dose-dependent manner. After treatment of wedelolactone, the expressions of collagen I and α-smooth muscle actin, two biomarkers of LX-2 activation, were remarkably decreased. The apoptosis of LX-2 cells was induced by wedelolactone accompanied with the decreasing expression of anti-apoptotic Bcl-2 and increasing expression of pro-apoptotic Bax. In addition, phosphorylated status of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) was up-regulated, but not in p38. Moreover, wedelolactone significantly repressed the level of phosphorylated inhibitor of nuclear factor κB (IκB) and p65 in nucleus in spite of tumor necrosis factor-α stimulation. In conclusion, wedelolactone could significantly inhibit the activation of LX-2 cells, the underlying mechanisms of which included inducing Bcl-2 family involved apoptosis, up-regulating phosphorylated status of ERK and JNK expressions, and inhibiting nuclear factor-κB (NF-κB) mediated activity. Wedelolactone might present as a useful tool for the prevention and treatment of hepatic fibrosis.

Avaliação da proteína acídica fibrilar glial como marcador da injúria por isquemia-reperfusão hepática

OBJETIVO: Avaliar a expressão da Proteína Acídica Fibrilar Glial após a injúria por isquemia-reperfusão. MÉTODOS: vinte e quatro ratos foram distribuídos em quatro grupos: Controle, submetidos à anestesia e biópsia hepática; Simulação, injeção de heparina através da veia cava e dissecção do pedículo hepático superior, biópsia após 24 horas; Isquemia 30 minutos, mesmo procedimento do grupo Simulação, acrescido de clampeamento do pedículo hepático superior por 30 minutos; Isquemia 90 minutos, mesmo procedimento do grupo Isquemia 30 minutos, porém com período de clampeamento de 90 minutos. Após 24 horas de observação, os animais foram submetidos à laparotomia e seus fígados avaliados macroscopicamente, microscopicamente, por coloração de Hematoxilina-Eosina (HE) e submetidos à análise da expressão da GFAP por Western Blotting. RESULTADOS: Não se observou diferença no aspecto macroscópico dos fígados entre os diferentes grupos experimentais, tendo todos evidenciado morfologia normal. A análise por HE não evidenciou diferenças significativas, no que diz respeito à morfologia lobular. Por outro lado, nos grupos isquemia, foram encontrados infiltrados neutrofílicos e pequenas áreas de necrose. A expressão de GFAP foi semelhante em todos os grupos, seja qualitativamente quanto quantitativamente. CONCLUSÃO: A expressão da Proteína Acídica Fibrilar Glial não se alterou em nosso modelo de isquemia-reperfusão.

P21-activated kinase-2 is a critical mediator of transforming growth factor-β-induced hepatoma cell migration

BACKGROUND AND AIM

Transforming growth factor-β (TGF-β) has been shown to play a central role in the promotion of cell motility, but its functional mechanism has remained unclear. With the aim of investigating the diagnostic and treatment modalities for patients with hepatocellular carcinoma (HCC), the signaling pathway that may contribute to TGF-β-mediated cell invasion in hepatoma cells was evaluated.

METHODS

Three hepatoma cell lines, HepG2, PLC/PRF/5, and HLF, were treated with TGF-β, and the involvement of the non-canonical TGF-β pathway was analyzed by cell migration assays. HepG2 cells were treated with a p21-activated kinase-2 (PAK2)-targeting small interfering RNA and analyzed for their cell motility. The relationships between the PAK2 status and the clinicopathological characteristics of 62 HCC patients were also analyzed.

RESULTS

The cell migration assays showed that Akt is a critical regulator of TGF-β-mediated cell migration. Western blotting analyses showed that TGF-β stimulated Akt and PAK2 in all three hepatoma cell lines, and phosphorylated PAK2 was blocked by Akt inhibitor. Suppression of PAK2 expression by small interfering RNA resulted in increased focal adhesions with significantly repressed cell migration in the presence of TGF-β. Clinicopathological analyses showed that the phosphorylation level of PAK2 was closely associated with tumor progression, metastasis, and early recurrence of HCC.

CONCLUSIONS

PAK2 may be a critical mediator of TGF-β-mediated hepatoma cell migration, and may represent a potential target for the treatment of HCC.

Migration of human dental follicle cells in vitro

BACKGROUND AND OBJECTIVES

The objective of this study was to elucidate the effects of different growth factors on the migration of dental follicle cells (DFCs). DFCs are ectomesenchymally derived easily accessible multipotent stem cells. Cell migration is a crucial step in many biological processes but also for tissue engineering. Growth factors such as epidermal growth factor (EGF), bone morphogenetic protein-2 (BMP2) or transforming growth factor β1 (TGF-β1) can be used to modify the behavior of cells.

MATERIAL AND METHODS

We used different migration assays (gel spot assay, scratch assay, transwell assay) to evaluate the influence of EGF, BMP2 and TGF-β1 on the migration of DFCs. We investigated the expression of migration-related genes after growth factor stimulation using the PCR array human cell motility.

RESULTS

DFCs treated with BMP2 or TGF-β1 migrated faster than DFCs treated with EGF. Additionally, more migration-related genes are regulated after treatment with BMP2 or TGF-β1 than with EGF. TGF-β1 additionally functions as a chemoattractant for DFCs. Osteogenic differentiation markers were regulated after BMP2 treatment only.

CONCLUSION

Whereas the strong migration induced by BMP2 was accompanied by beginning osteogenic differentiation the strong migration induced by TGF-β1 was directional. EGF exhibited not only the weakest migration stimulation but also the weakest induction of differentiation into mineralizing cells.

Bone marrow cell transplantation is associated with fibrogenic cells apoptosis during hepatic regeneration in cholestatic rats

Liver fibrosis is accompanied by hepatocyte death and proliferation of α-SMA+ fibrogenic cells (activated hepatic stellate cells and myofibroblasts), which synthesize extracellular matrix components that contribute to disorganization of the hepatic parenchyma and loss of liver function. Therefore, apoptosis of these fibrogenic cells is important to hepatic regeneration. This study aimed to analyze the effect of cell therapy using bone marrow mononuclear cell (BMMNC) transplantation on α-SMA expression and on apoptosis of hepatic cells during liver fibrosis induced by bile duct ligation (BDL). Livers were collected from normal rats, fibrotic rats after 14 and 21 days of BDL, and rats that received BMMNC at 14 days of BDL and were analyzed after 7 days. Apoptosis in fibrogenic cells was analyzed by immunoperoxidase, confocal microscopy, and Western blotting, and liver regeneration was assessed by proliferating cell nuclear antigen staining. Results showed that caspase-3 and proliferating cell nuclear antigen expression were significantly increased in the BMMNC-treated group. Additionally, confocal microscopy analysis showed cells coexpressing α-SMA and caspase-3 in these animals, suggesting fibrogenic cell death. These results suggest a novel role for BMMNC in liver regeneration during fibrotic disease by stimulating fibrogenic cells apoptosis and hepatocyte proliferation, probably through secretion of specific cytokines that modulate the hepatic microenvironment toward an antifibrogenic balance.

The antihepatic fibrotic effects of fluorofenidone via MAPK signalling pathways

BACKGROUND

Fluorofenidone (AKF-PD) is a novel pyridone agent. The purpose of this study is to investigate the inhibitory effects of AKF-PD on dimethylnitrosamine (DMN)-induced liver fibrosis in rats and the involved molecular mechanism related to hepatic stellate cells (HSCs).

MATERIALS AND METHODS

Wistar rats were randomly divided into normal control, DMN, DMN/AKF-PD treatment and DMN/pirfenidone (PFD) treatment groups. AKF-PD and PFD treatments were, respectively, performed for two activated HSCs lines, rat CFSC-2G and human LX2. The cell proliferation was analysed by MTT. The expression of collagen I was determined by immunohistochemical staining and real-time RT-PCR. The expression of α-smooth muscle actin (α-SMA), tissue inhibitor of metalloproteinases-1 (TIMP-1), extracellular signal regulated kinase (ERK1/2), p38 MAPK (p38), and c-Jun N-terminal kinase/stress-activated protein kinase (JNK) were also detected by real-time RT-PCR and/or Western blot.

RESULTS

AKF-PD significantly reduced PDGF-BB-induced proliferation and activation of HSCs, as determined by reducing protein expression of α-SMA and TIMP-1. AKF-PD treatment attenuated PDGF-BB-induced upregulation of phosphorylation of ERK1/2, p38 and JNK. In fibrotic rat liver, AKF-PD reduced the degree of liver injury and hepatic fibrosis, which was associated with reduced the expression of collagen I, α-SMA, TIMP-1 at both mRNA and protein levels.

CONCLUSION

AKF-PD treatment inhibits the progression of hepatic fibrosis by suppressing HSCs proliferation and activation via MAPK signalling pathway.

MicroRNA-21 activates hepatic stellate cells via PTEN/Akt signaling

Activation of hepatic stellate cells is the key event in the liver fibrosis. miRs have been shown to play fundamental role in diverse biological and pathological processes. In the present study, we investigated the fibrogenic role of miR-21 in human hepatic stellate LX-2 cells and explored underlying mechanisms. The results showed that treatment of LX-2 cells with platelet-derived growth factor (PDGF)-BB significantly stimulated α1(I) collagen mRNA synthesis and the protein expression of α-SMA, which are characteristics of activation of hepatic stellate cells and simultaneously increased miR-21 expression. Downregulation of miR-21 expression by transfection of anti-miR-21 into LX-2 cells prevented PDGF-BB-induced LX-2 cell activation. Overexpression of miR-21 expression alone also stimulated LX-2 cell activation, while downregulation of miR-21 expression suppressed LX-2 cell activation. miR-21 also played a role in mRNA expression and activity of matrix metalloproteinase 2 (MMP2) in LX-2 cells. Moreover, overexpression of miR-21 decreased protein expression of PTEN in LX-2 cells, resulting in activation of the Akt. Inhibition of Akt signaling by specific inhibitor LY 294002 blocked miR-21-induced fibrogenic effects in LX-2 cells. In summary, miR-21 is an important mediator in LX-2 cell activation. The fibrogenic effects of miR-21 on LX-2 cell activation are mediated through PTEN/Akt pathway. miR-21 may be a potential novel molecular target for the liver fibrosis.

Inhibition of TGF-β signaling enables human corneal endothelial cell expansion in vitro for use in regenerative medicine

Corneal endothelial dysfunctions occurring in patients with Fuchs' endothelial corneal dystrophy, pseudoexfoliation syndrome, corneal endotheliitis, and surgically induced corneal endothelial damage cause blindness due to the loss of endothelial function that maintains corneal transparency. Transplantation of cultivated corneal endothelial cells (CECs) has been researched to repair endothelial dysfunction in animal models, though the in vitro expansion of human CECs (HCECs) is a pivotal practical issue. In this study we established an optimum condition for the cultivation of HCECs. When exposed to culture conditions, both primate and human CECs showed two distinct phenotypes: contact-inhibited polygonal monolayer and fibroblastic phenotypes. The use of SB431542, a selective inhibitor of the transforming growth factor-beta (TGF-β) receptor, counteracted the fibroblastic phenotypes to the normal contact-inhibited monolayer, and these polygonal cells maintained endothelial physiological functions. Expression of ZO-1 and Na⁺/K⁺-ATPase maintained their subcellular localization at the plasma membrane. Furthermore, expression of type I collagen and fibronectin was greatly reduced. This present study may prove to be the substantial protocol to provide the efficient in vitro expansion of HCECs with an inhibitor to the TGF-β receptor, and may ultimately provide clinicians with a new therapeutic modality in regenerative medicine for the treatment of corneal endothelial dysfunctions.

Cannabinoid receptors as therapeutic targets for dialysis-induced peritoneal fibrosis

BACKGROUND

Long-term exposure to bioincompatible peritoneal dialysis solutions is frequently complicated with peritoneal fibrosis and ultrafiltration failure. As cannabinoid receptor (CBR) ligands have been reported to be beneficial to ameliorate the process of liver fibrosis, we strove to investigate their therapeutic potential to prevent peritoneal fibrosis.

METHODS

We used the rat model of peritoneal fibrosis induced by intraperitoneal injection of methylglyoxal and in vitro mesothelial cell culture to test the effects of CBR ligands, including the type 1 CBR (CB(1)R) antagonist and the type 2 CBR (CB(2)R) agonist.

RESULTS

In the methylglyoxal model, both intraperitoneal CB(1)R antagonist (AM281) and CB(2)R agonist (AM1241) treatment significantly ameliorated peritoneal fibrosis. In addition, CB(1)R antagonist was able to alleviate TGF-β(1)-induced dedifferentiation of mesothelial cells and to maintain epithelial integrity in vitro.

CONCLUSIONS

Intraperitoneal administration of CBR ligands (CB(1)R antagonist and CB(2)R agonist) offers a potential therapeutic strategy to reduce dialysis-induced peritoneal fibrosis and to prolong the peritoneal survival in peritoneal dialysis patients.

Curcumin and liver disease

Liver diseases pose a major medical problem worldwide and a wide variety of herbs have been studied for the management of liver-related diseases. In this respect, curcumin has long been used in traditional medicine, and in recent years it has been the object of increasing research interest. In combating liver diseases, it seems clear that curcumin exerts a hypolipidic effect, which prevents the fatty acid accumulation in the hepatocytes that may result from metabolic imbalances, and which may cause nonalcoholic steatohepatitis. Another crucial protective activity of curcumin, not only in the context of chronic liver diseases but also regarding carcinogenesis and other age-related processes, is its potent antioxidant activity, which affects multiple processes and signaling pathways. The effects of curcumin on NF-κβ are crucial to our understanding of the potent hepatoprotective role of this herb-derived micronutrient. Because curcumin is a micronutrient that is closely related to cellular redox balance, its properties and activity give rise to a series of molecular reactions that in every case and biological situation affect the mitochondria.

Attenuation of hepatic fibrosis by an imidazolium salt in thioacetamide-induced mouse model

BACKGROUND AND AIM

Hepatic fibrosis is a worldwide healthy burden associated with significant morbidity and mortality. It is caused by a variety of chronic liver injuries. There is currently no effective treatment for liver fibrosis. In this report, we tested an imidazolium salt, 1,3-diisopropylimidazolium tetrafluoroborate (DPIM), for its anti-fibrotic properties in the thioacetamide-induced mouse model.

METHODS

DPIM was orally delivered to the thioacetamide-treated mice via drinking water for 12 weeks at the onset of thioacetamide treatment at a concentration of 0.1% (prevention group), and for 4 weeks starting at the 8(th) week at a concentration of 0.1% or 0.2% (attenuation group), respectively. Messenger RNA and protein were determined by real-time polymerase chain reaction and Western blotting, matrix metalloproteinase (MMP) activities were measured by fluorogenic peptide substrate and zymography. Mitogen-activated protein kinase (MAPK) and PI3K inhibitors were applied in HSC-T6 cells in combination of DPIM to probe possible signal pathways underlying the compound's action.

RESULTS

We observed a significant reduction in collagen deposition in both prevention and attenuation groups. The α-smooth muscle actin (SMA) and transforming growth factor (TGF)-β gene expressions were also reduced in both groups. The reduction of collagen deposition could be in part attributed to the suppression of CCR-2 expression and the enhanced matrix protein remodeling by metalloproteinases, especially MMP-3. MAPK and PI3K signaling pathways may be partially participated in DPIM's molecular action.

CONCLUSION

DPIM reduced fibrosis in the thioacetamide-induced mouse liver fibrosis model, and warranted further studies for possible clinical application in the future.

Hepatitis C virus and hepatocarcinogenesis

Hepatitis C virus (HCV) is an RNA virus that is unable to integrate into the host genome. However, its proteins interact with various host proteins and induce host responses. The oncogenic process of HCV infection is slow and insidious and probably requires multiple steps of genetic and epigenetic alterations, the activation of cellular oncogenes, the inactivation of tumor suppressor genes, and dysregulation of multiple signal transduction pathways. Stellate cells may transdifferentiate into progenitor cells and possibly be linked to the development of hepatocellular carcinoma (HCC). Viral proteins also have been implicated in several cellular signal transduction pathways that affect cell survival, proliferation, migration and transformation. Current advances in gene expression profile and selective messenger RNA analysis have improved approach to the pathogenesis of HCC. The heterogeneity of genetic events observed in HCV-related HCCs has suggested that complex mechanisms underlie malignant transformation induced by HCV infection. Considering the complexity and heterogeneity of HCCs of both etiological and genetic aspects, further molecular classification is required and an understanding of these molecular complexities may provide the opportunity for effective chemoprevention and personalized therapy for HCV-related HCC patients in the future. In this review, we summarize the current knowledge of the mechanisms of hepatocarcinogenesis induced by HCV infection.

Inhibitory effects of salvianolic acid B on CCl(4)-induced hepatic fibrosis through regulating NF-κB/IκBα signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatic fibrosis, a precursor of liver cirrhosis, is a consequence of severe liver damage that occurs in many patients with chronic liver diseases. Salvianolic acid B (SA-B) is one of water soluble compounds derived from Salvia miltiorrhiza Bunge (Danshen in Chinese) widely used for chronic liver diseases. In this study we investigated the protective effects of SA-B on CCl(4)-induced hepatic fibrosis.

MATERIALS AND METHODS

Hepatic fibrosis in rats was induced by carbon tetrachloride (CCl(4)). Rats were divided into four groups, including normal controls (N group), model (M group), low SA-B of 10mg/kg body weight (L group), or high SA-B of 20mg/kg body weight (H group). After 6 weeks, macroscopic features of the liver and weight ratio of liver to body were measured. Liver fibrosis of the rats was evaluated by HE and Massion staining. Activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL) were checked with automated biochemistry analyzer. Serum levels of hyaluronic acid (HA), type IV collagen (IV-C), Laminin (LN) and procollagen III peptide (PIIIP) were detected by radioimmunoassay (RIA). The expression of NF-κB and IκBα was detected by western blotting.

RESULTS

SA-B was shown to reduce CCl(4)-induced hepatic fibrosis in rats. The serum levels of ALT, AST, and TBIL were significantly lower in the SA-B treatment groups than in the M group. Compared the M group, the serum levels of HA, LN, IV-C and PIIIP were decreased markedly after treatment with SA-B, especially in the H group. Treatment with SA-B at 10-20mg/kg (L and N groups, respectively) dose-dependently decreased the expression of NF-κB in the nucleolus and increased the expression levels of NF-κB and IκBα protein in the cytoplasm compared to that of the M group.

CONCLUSIONS

This study reveals that SA-B could prevent the progression of liver angiogenesis and alleviate liver fibrosis possibly by regulating the expression of NF-κB and IκBα.

Puerarin mediates hepatoprotection against CCl4-induced hepatic fibrosis rats through attenuation of inflammation response and amelioration of metabolic function

This study was designed to evaluate the potential effects of puerarin (PR), an effective isoflavonoid compound purified from Pueraria lobata, in treating hepatic fibrosis (HF) rats induced by carbon tetrachloride (CCl(4), 2 mL kg(-1) d(-1)). Compared to model control, PR treatment effectively lowered the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (Alb), total protein (TP) in HF rats. Masson stained analysis showed that the condition of HF rats was mitigated. Meanwhile, the tumor necrosis factor alpha (TNF-α), nuclear factor-kappa B (NF-κB) expressions were significantly down-regulated at protein level by PR intervention. Additionally, the activity of superoxide dismutase (SOD) was elevated, while the content of malondialdehyde (MDA) was lessened in liver tissue. As revealed by immunohistochemistry assay, PR therapy resulted in reduced production of transforming growth factor-βl (TGF-βl). Moreover, it also was attributed to decreased mRNA level of inducible nitric oxide synthase (iNOS) using RT-PCR analysis. These findings demonstrate that puerarin successfully reverses hepatotoxicity in CCl(4)-induced HF rats via the underlying mechanisms of regulating serum enzymes and attenuating TNF-α/NF-κB pathway for anti-inflammation response, as well as improving metabolic function in liver tissue.

Elevation of alanine transaminase and markers of liver fibrosis after a mixed meal challenge in individuals with type 2 diabetes

BACKGROUND

Hyperalimentation for 4 weeks is associated with raised liver enzymes and liver fat content (LFC), which are two common features found in individuals with diabetes.

AIM

We evaluated the effect of two mixed meal challenges on LFC, liver enzymes and serum bio-markers of liver injury and fibrosis in 16 healthy volunteers (HV) and subjects with type 2 diabetes (T2DM).

METHODS

Subjects (HV: 9 male, 7 female, aged 57.9 ± 1.7 years, body mass index (BMI) 27.1 kg/m(2); and T2DM: 11 male, 5 female, aged 62.1 ± 1.3 years, BMI 28.0 ± 0.4 kg/m(2)) consumed two meals at 1 h (884 kcal) and at 6 h (1,096 kcal). LFC determined by (1)H magnetic resonance spectroscopy, serum levels of liver enzymes, hyaluronic acid (HA), procollagen III N-terminal peptide (P3NP) and tissue inhibitor metalloproteinase-1 (TIMP-1) were estimated at time 0 (fasting) and 9 h (postprandial).

RESULTS

Fasting LFC was higher in the T2DM group 7.6 % (4.9, 15.4) [median (inter-quartile range)] than in the HV group 2.3 % (0.8, 5.1) (p < 0.05) while levels of HA, P3NP and TIMP-1 were similar. Following the meal challenge there was no significant change in LFC. Subjects with T2DM had higher post-prandial rise in alanine transaminase (ALT) (p = 0.014), serum HA (p = 0.007) and P3NP (p = 0.015) compared with HV. Fasting LFC correlated with a greater post-prandial increase in P3NP levels in all subjects (Pearson correlation r = 0.53, p = 0.001).

CONCLUSIONS

In subjects with T2DM, a mixed meal challenge is associated with a significant elevation in the serum levels of ALT, HA and P3NP without significant changes in LFC. These markers should be performed in the fasted state.

Effect and mechanism of methyl helicterate isolated from Helicteres angustifolia (Sterculiaceae) on hepatic fibrosis induced by carbon tetrachloride in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Methyl helicterate is a triterpenoid isolated from Helicteres angustifolia (Sterculiaceae), one of the valuable traditional Chinese herbs. Antifibrotic activities of H. angustifolia have been extensively proved.

AIM OF THE STUDY

The purpose of this study was to investigate the effect of methyl helicterate (MH) on liver fibrosis in rats induced by carbon tetrachloride (CCl(4)) and to explore its underlying mechanism.

MATERIALS AND METHODS

Hepatic fibrosis was induced in male Sprague-Dawley (SD) rats by intragastric administration with 2 ml/kg CCl(4) (mixed 1:1 in peanut oil) twice a week for 12 weeks. To evaluate the effect of MH (16.72, 33.45, 66.90 mg/kg) on hepatic fibrosis, liver function, histological study and hepatic fibrosis evaluation were performed. Liver function was assessed by determining the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (Alb) and total protein (TP). The biomarkers such as hydroxyproline (Hyp), hyaluronic acid (HA), type III precollagen (PCIII) and laminin (LN) were examined for the evaluation of hepatic fibrosis. The underlying mechanism was investigated by measuring oxidative stress level and detecting the expression of TGF-β1 mRNA and Smad3 protein.

RESULTS

MH (33.45, 66.90 mg/kg) treatment significantly inhibited the loss of body weight and the increase of liver index in rats induced by CCl(4). MH also improved the liver function as indicated by decreasing serum enzymatic activities of ALT, AST, TP and Alb (P<0.05). Histological results indicated that MH alleviated liver damage and reduced the formation of fibrous septa. Moreover, MH significantly decreased liver Hyp, HA, LN and PCIII (P<0.05). Research on mechanism showed that MH could markedly reduce liver malondialdehyde (MDA) concentration, increase activities of liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and inhibit the expression of TGF-β1 mRNA and Smad3 protein (P<0.05).

CONCLUSIONS

Our findings indicated that MH can inhibit CCl(4)-induced hepatic fibrosis, which may be ascribed to its radical scavenging action, antioxidant activity, and modulation of TGF-β-Smad3 signaling pathway.

GW501516-activated PPARβ/δ promotes liver fibrosis via p38-JNK MAPK-induced hepatic stellate cell proliferation

BACKGROUND

After liver injury, the repair process comprises activation and proliferation of hepatic stellate cells (HSCs), which produce extracellular matrix (ECM) proteins. Peroxisome proliferator-activated receptor beta/delta (PPARβ/δ) is highly expressed in these cells, but its function in liver repair remains incompletely understood. This study investigated whether activation of PPARβ/δ with the ligand GW501516 influenced the fibrotic response to injury from chronic carbon tetrachloride (CCl4) treatment in mice. Wild type and PPARβ/δ-null mice were treated with CCl4 alone or CCl4 co-administered with GW501516. To unveil mechanisms underlying the PPARβ/δ-dependent effects, we analyzed the proliferative response of human LX-2 HSCs to GW501516 in the presence or absence of PPARβ/δ.

RESULTS

We found that GW501516 treatment enhanced the fibrotic response. Compared to the other experimental groups, CCl4/GW501516-treated wild type mice exhibited increased expression of various profibrotic and pro-inflammatory genes, such as those involved in extracellular matrix deposition and macrophage recruitment. Importantly, compared to healthy liver, hepatic fibrotic tissues from alcoholic patients showed increased expression of several PPAR target genes, including phosphoinositide-dependent kinase-1, transforming growth factor beta-1, and monocyte chemoattractant protein-1. GW501516 stimulated HSC proliferation that caused enhanced fibrotic and inflammatory responses, by increasing the phosphorylation of p38 and c-Jun N-terminal kinases through the phosphoinositide-3 kinase/protein kinase-C alpha/beta mixed lineage kinase-3 pathway.

CONCLUSIONS

This study clarified the mechanism underlying GW501516-dependent promotion of hepatic repair by stimulating proliferation of HSCs via the p38 and JNK MAPK pathways.

Cardiomyocyte ATP release through pannexin 1 aids in early fibroblast activation

Fibrosis following myocardial infarction is associated with increases in arrhythmias and sudden cardiac death. Initial steps in the development of fibrosis are not clear; however, it is likely that cardiac fibroblasts play an important role. In immune cells, ATP release from pannexin 1 (Panx1) channels acts as a paracrine signal initiating activation of innate immunity. ATP has been shown in noncardiac systems to initiate fibroblast activation. Therefore, we propose that ATP release through Panx1 channels and subsequent fibroblast activation in the heart drives the development of fibrosis in the heart following myocardial infarction. We identified for the first time that Panx1 is localized within sarcolemmal membranes of canine cardiac myocytes where it directly interacts with the postsynaptic density 95/Drosophila disk large/zonula occludens-1-containing scaffolding protein synapse-associated protein 97 via its carboxyl terminal domain (amino acids 300-357). Induced ischemia rapidly increased glycosylation of Panx1, resulting in increased trafficking to the plasma membrane as well as increased interaction with synapse-associated protein 97. Cellular stress enhanced ATP release from myocyte Panx1 channels, which, in turn, causes fibroblast transformation to the activated myofibroblast phenotype via activation of the MAPK and p53 pathways, both of which are involved in the development of cardiac fibrosis. ATP release through Panx1 channels in cardiac myocytes during ischemia may be an early paracrine event leading to profibrotic responses to ischemic cardiac injury.