Molecular mechanisms of hepatic fibrogenesis

Improved muscle strength and mobility in the dy(2J)/dy(2J) mouse with merosin deficient congenital muscular dystrophy treated with Glatiramer acetate

The therapeutic effect of Glatiramer acetate, an immune modulating agent, was evaluated in the dy(2J)/dy(2J) mouse with merosin deficient congenital muscular dystrophy, which is a milder variant of the dy/dy mouse. The treated mice showed significant improvement in hind limb muscle strength measured by electronic grip strength meter and in motor performance quantified by video detection software. Glatiramer acetate treatment was associated with significantly increased expression of regeneration transcription factors MyoD and myogenin, and attenuation of the fibrosis markers vimentin and fibronectin. No effective treatment is currently available in congenital muscular dystrophy and Glatiramer acetate may present a new potential treatment for this disorder.

Selenium supplementation attenuates procollagen-1 and interleukin-8 production in fat-loaded human C3A hepatoblastoma cells treated with TGFbeta1

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance and hepatic steatosis. Non-alcoholic steatohepatitis (NASH) is a serious consequence of NAFLD where chronic tissue damage and inflammation result in fibrosis which may progress to cirrhosis. Transforming growth factor beta1 (TGFbeta1), proinflammatory cytokines and oxidative stress are thought to play crucial roles in the pathogenesis of these conditions. The contributions of individual liver cell types to fibrogenesis remain controversial and the influence of selenium status has not been investigated.

METHODS

In this study we have used a cell culture model of fat-loading using oleate-treated human hepatoblastoma (C3A) cells to investigate how fat-loading and selenium status might influence the production of collagen in response to TGFbeta1. The secretion of inflammatory cytokines was also investigated, together with the epithelial character of the treated cells.

RESULTS

We found that in response to treatment with TGFbeta1, C3A cells produced mRNA encoding the pro-alphaI chain of procollagen I, secreted procollagen I peptide, up-regulated production of the proinflammatory cytokine interleukin-8 (IL-8) and the mesenchymal marker vimentin, and down-regulated albumin production. Most of these responses were considerably enhanced when cells were fat-loaded with oleate and were attenuated by selenium addition at a dose that optimised the expression of thioredoxin reductase and glutathione peroxidase.

CONCLUSIONS

Our data establish that both fat-loading and suboptimal selenium status enhance collagen and IL-8 production by C3A hepatocytes in response to TGFbeta1, possibly as part of an epithelial to mesenchymal transition.

GENERAL SIGNIFICANCE

These findings suggest that the hepatocyte may be an important contributor to the pathogenesis of fibrosis associated with NAFLD.

Coronary flow reserve is impaired in patients with nonalcoholic fatty liver disease: association with liver fibrosis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of cardiovascular disease. Coronary flow reserve (CFR) is widely used to examine the integrity of coronary microvascular circulation. We evaluated the prevalence of impaired CFR in patients with biopsy-proven NAFLD. We also investigated the independent clinical, biochemical, and liver histology predictors of CFR in the setting of NAFLD.

METHODS

Fifty-nine consecutive patients with NAFLD and 77 age- and gender-matched controls were evaluated. CFR recordings were performed by transthoracic Doppler harmonic echocardiography. CFR>or=2.0 was considered normal.

RESULTS

CFR was significantly lower in patients with NAFLD than in controls (2.11+/-0.45 vs. 2.52+/-0.62, P<0.001). An impaired CFR (i.e. <2) was found in 25 NAFLD patients (42.4%) whereas all controls had normal CFR values (P<0.001). A stepwise linear regression analysis in NAFLD patients identified liver fibrosis scores as the only independent predictor of CFR values (beta=-0.60; t=-2.44, P=0.021).

CONCLUSION

Our findings indicate that in patients with biopsy-proven NAFLD: (a) an abnormal CFR is found in approximately 42.4% of cases, and (b) liver fibrosis scores are an independent predictor of depressed CFR.

Role of angiotensin II in liver fibrosis-induced portal hypertension and therapeutic implications

Angiotensin II (AT-II) is a peptide that plays an important role in the renin-angiotensin-aldosterone (RAA) system. Traditionally, the RAA system has been related with states of systemic hypertension and hypoperfusion as a counterbalance mechanism. Recently, AT-II has been studied for its properties in the process of fibrosis in several organs, especially in the liver. AT-II is capable to stimulate the activated hepatic stellate cells, which increase expression of profibrogenic molecules like tumor growth factor-beta, tissue inhibitor of metalloproteinase-1 and collagen I, among others. At the same time, AT-II is implied in the hemodynamic balance of cirrhosis and portal hypertension. Due to its profibrogenic and vasoactive properties, blockade of AT-II actions constitutes an important therapeutic target to inhibit fibrotic processes and reduction of risk of complications of portal hypertension as well. Some drugs like angiotensin-converting enzyme inhibitors or the angiotensin II receptor blockers have been studied as alternatives for the treatment of patients with cirrhosis with promising results. Nonetheless, additional research is required in order to consider these drugs as a part of the integral treatment of the patient with cirrhosis and portal hypertension.

Toll-like receptor activated human and murine hepatic stellate cells are potent regulators of hepatitis C virus replication

BACKGROUND/AIMS

While hepatic stellate cells (HSC) are known to be key mediators of liver fibrosis, only little is known about their functional role in the innate immune system of the liver.

METHODS

To address this question, murine HSC were isolated from livers of C57BL/6J mice and human HSC were isolated from liver samples obtained from resections and liver explants. HSC were stimulated with Toll-like receptor (TLR) 1-9 ligands for 20 h. Supernatants were harvested and used in virus protection assays (encephalomyocarditis virus, EMCV) as well as in human and murine hepatitis C virus (HCV) replicon systems. Expression of interferon (IFN), retinoic acid-inducible gene-I (RIG-I), and interferon-stimulated genes (ISGs) was assessed by quantitative reverse transcription polymerase chain reaction.

RESULTS

While all TLRs were detectable in HSC, in murine HSC only TLR 3 and -4 agonists could induce cytokines that had an antiviral effect upon EMCV and HCV replication. IFN-beta was the main cytokine mediating the antiviral activity of TLR 3-stimulated HSC whereas other cytokines of undefined nature were involved in TLR 4-mediated antiviral effects. In human HSC, only TLR 3 stimulation led to production of antiviral cytokines. The antiviral effect was related to the up-regulation of ISGs and RIG-I in target cells.

CONCLUSIONS

These data demonstrate that murine and human HSC have as yet unrecognized antiviral properties when activated through the TLR-system and TLR 3/HCV in particular. This sheds new light on their role in the innate immune system of the liver and their participation in the control of HCV replication.

PTEN expression is down-regulated in liver tissues of rats with hepatic fibrosis induced by biliary stenosis

The gene phosphatase and tensin homolog deleted on chromosome 10 (PTEN) codes for a tumor-suppressor phospholipid phosphatase. Deletion, mutation or abnormal expression of PTEN is commonly found in many kinds of malignant tumors. At the time of this study, though, the role of PTEN expression in the pathology of hepatic fibrosis remains unclear. In this study, we investigate the dynamic expression of PTEN in a rat model of hepatic fibrosis, with special emphasis on the activation and proliferation of hepatic stellate cells (HSC) in vivo. The rat model of hepatic fibrosis used in this study employed common bile duct ligation. At four time points, the expression of PTEN in hepatic tissues and activated HSC in rat liver tissues was measured by immunohistochemical staining, Western blotting, real-time fluorescent quantitative PCR and immunofluorescence confocal laser scanning microscopy, respectively. Further, alpha-smooth muscle actin (alpha-SMA), an activated HSC marker in rat liver tissues, was detected by immunohistochemical staining. This study showed that aggravation of hepatic fibrosis led to gradually decreasing expression of PTEN in the hepatic tissues. Further, as hepatic fibrosis worsens, PTEN-expressing activated HSC accounts for an increasingly smaller percentage of all activated HSC. In contrast, the percentage of alpha-SMA-expressing HSC cells increases significantly. In conclusion, expression of PTEN mRNA and protein is down-regulated in fibrogenic rat liver tissue, and its expression in HSC in vivo also decreases with progression of fibrosis. Thus, these results show that the dynamic expression of PTEN in hepatic tissues negatively correlates with activation and proliferation of HSC.

A complex role of activin A in non-alcoholic fatty liver disease

OBJECTIVES

Recent studies suggest that activin A, a member of the transforming growth factor (TGF) superfamily, is involved in the pathogenesis of liver disorders. We sought to explore its possible role in non-alcoholic fatty liver disease (NAFLD).

METHODS

Serum levels of activin A and its natural inhibitor, follistatin, were measured in patients with NAFLD (n=70) and in control subjects (n=30). Gene expression was quantified in liver biopsies obtained from patients with NAFLD (n=13) and controls (n=6). Effects of activin A were examined in Huh7 (human hepatoma cell line) hepatocytes.

RESULTS

Patients with NAFLD had significantly elevated serum levels of activin A and follistatin compared with healthy controls. In patients with non-alcoholic steatohepatitis (NASH, n=38), there were particularly high levels of activin A that were significantly related to the degree of hepatic fibrosis. Liver biopsies from NAFLD patients showed a markedly increased activin A-follistatin mRNA ratio, indicating increased hepatic activin A activity. In hepatocytes, activin A enhanced the expression of collagen and TGF-beta(1), promoted matrix metalloproteinase activity, induced mitochondrial beta-oxidation, downregulated fatty acid (FA) synthase activity, promoted decreased weight percentage of saturated FAs, and altered the composition of polyunsaturated FAs.

CONCLUSIONS

Our findings support the complex role of activin A in the pathogenesis of NAFLD, involving effects on fibrosis and lipid accumulation.

Role of host genetic factors in the outcome of hepatitis C virus infection

The natural history of hepatitis C virus (HCV) infection is determined by a complex interplay between host genetic, immunological and viral factors. This review highlights genes involved in innate and adaptive immune responses associated with different outcomes of HCV infection. For example, an association of HCV clearance with certain HLA alleles has been demonstrated. The mechanisms responsible for these associations have been linked to specific T cell responses for some particular alleles (e.g., HLA-B27). Genetic associations involved in T cell regulation and function further underline the role of the adaptive immune response in the natural history of HCV infection. In addition, some genes involved in innate NK cell responses demonstrate the complex interplay between components of the immune system necessary for a successful host response to HCV infection.

Loss of steroid receptor co-activator-3 attenuates carbon tetrachloride-induced murine hepatic injury and fibrosis

Hepatic fibrosis, a disease characterized by altered accumulation of extracellular matrix, can cause cirrhosis and liver failure. There is growing interest in the impact of co-activators on hepatic fibrogenesis. Here, we provided genetic evidence that mice lacking steroid receptor co-activator-3 (SRC-3) were protected against carbon tetrachloride (CCl4)-induced acute liver necrosis and chronic hepatic fibrosis. After acute CCl4 treatment, SRC-3(-/-) mice showed attenuated profibrotic response and hepatocyte apoptosis, whereas hepatocyte proliferation was elevated in SRC-3(-/-) mice versus SRC-3+/+ mice. Similarly, chronically CCl4-treated SRC-3(-/-) mice showed significant weakening of inflammatory infiltrates, hepatic stellate cell activation and collagen accumulation in the liver compared with SRC-3+/+ mice. Further investigation revealed that TGFbeta1/Smad signaling pathway was impaired in the absence of SRC-3. Moreover, the expression levels of SRC-3, as assessed in human tissue microarray of liver diseases, correlated positively with degrees of fibrosis. These data revealed that SRC-3(-/-) mice were resistant to CCl4-induced acute and chronic hepatic damage and TGFbeta1/Smad signaling was suppressed in the lack of SRC-3. Our results established an essential involvement of SRC-3 in liver fibrogenesis, which might provide new clues to the future treatment of hepatic fibrosis.

Insulin-like growth factor binding protein-7 induces activation and transdifferentiation of hepatic stellate cells in vitro

AIM: To investigate the role of insulin-like growth factor binding protein-7 (IGFBP-7) in the activation and transdifferentiation of hepatic stellate cells (HSC) in vitro.

METHODS: Rat HSC-T6 cells were cultured in separate dishes and treated with various concentration of transforming growth factor (TGF)-β₁, IGFBP-7 or anti-IGFBP-7 antibody for 24 h. The supernatant or a cytoplasm suspension was obtained from cultured HSC, followed by transfer of cells to form cell-coated dishes. Immunocytochemistry and Western blotting were used to analyze the expression of IGFBP-7 induced by TGF-β₁ and the level of fibronectin, collagen I and α-smooth muscle actin (SMA). The pro-apoptotic effect of anti-IGFBP-7 antibody was determined by flow cytometry.

RESULTS: Immunocytochemistry and Western blotting revealed that the expression of IGFBP-7 in TGF-β₁ treated HSC was significantly up-regulated compared to that in the control group. In addition, fibronectin, collagen I and α-SMA also showed enhanced expression in accordance with the transdifferentiation process in a dose-dependent manner to some extent. Moreover, flow cytometry suggested that anti-IGFBP-7 antibody induced apoptosis of activated HSC, which is responsible for the development of liver fibrosis, and may represent a novel pathway and target for therapeutic intervention.

CONCLUSION: IGFBP-7 showed increased expression in activated HSC and played an important role in the activation and transdifferentiation process of HSC. Anti-IGFBP-7 antibody may ameliorate liver fibrogenesis.

Effects of chelerythine on hepatic TGF-β1 and α-SMA expression in rats with hepatic fibrosis

AIM: To study the effects of chelerythine on TGF-β1 and α-SMA expression of CCl₄ -induced hepatic fibrosis in rats.

METHODS: Models of hepatic fibrosis were established by hypodermic injection of tetrachloride, in combination with the control of nutrition and the drinking of 100 mL/L alcohol to rats. According to histological sections, hepatic fibrosis in rats emerged at the end of the fourth week. Subsequently different doses of chelerythine were used of hepatic fibrosis in rats. In addition, normal control group, fibrotic model group, γ-interform group in experiment was arranged. At the end of the eighth week, all the rats were executed. Transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) in liver were examined with the immunohistochemistrical technique.

RESULTS: The expression of TGF-β1 and α-SMA in liver of rats in fibrotic model group induced by CCl₄ were ameliorated significantly compared with the model group (TGF-β1: 6.08 ± 2.35, 4.31 ± 2.10, 4.7 ± 1.70 vs 9.33 ± 3.08; α-SMA: 3.75 ± 1.76, 3.23 ± 1.42, 3.20 ± 1.17 vs 6.67 ± 2.29, all P < 0.01). The expression of TGF-β1 and α-SMA in liver was not obviously different between all chelerythine groups and γ-INF group (4.23 ± 2.24, 3.38 ± 1.39, both P > 0.05).

CONCLUSION: Chelerythine can decrease the expression of TGF-β1 as well as α-SMA CCl4 -induced hepatic fibrosis in rats.

Influence of heme oxygenase-1 expression on immune liver fibrosis induced by cobalt protoporphyrin in rats

AIM: To investigate the effect of heme oxygenase-1 (HO-1) expression on immune liver fibrosis induced by cobalt protoporphyrin (CoPP) in rats.

METHODS: An immune liver fibrosis model of rat was established by administering human serum albumin (HSA). The rats were divided into CoPP, liver fibrosis and normal control groups. Rats in the CoPP group received intraperitoneal CoPP concurrently with HSA. Expression of HO-1 protein was observed by Western blotting and immunohistochemistry. Hematoxylin and eosin (HE) staining was performed to assess fibrosis proliferation and distribution, proliferation extent of fibroblasts, and alterations in hepatocytes and inflammatory cells. Type I and III collagens were detected with Van Gieson’s (VG) staining and Foot’s reticular fiber staining, respectively. In addition, spindle-shaped cells existing at perisinusoidal locations beyond portal and septa areas were investigated with HE staining.

RESULTS: Western blotting and immunohistochemistry showed that the expression of HO-1 protein was higher in the CoPP group than in the liver fibrosis group (P < 0.05). Compared with the liver fibrosis group, the serological index of hepatic fibrosis in the CoPP group decreased significantly (P < 0.05). HE, VG and Foot’s staining revealed that administration of CoPP reduced the extent of hepatic fibrosis. The levels of serological indicators and the number of spindle-shaped cells at perisinuous locations beyond the portal and septa areas were reduced in the CoPP group. Only a few inflammatory cells were seen around the portal areas and central veins in the CoPP group.

CONCLUSION: Increased endogenous HO-1 may suppress liver fibrosis by protecting liver cells, inhibiting inflammatory cell infiltration and hepatic stellate cell transformation.

Emerging concepts in the pathogenesis of lung fibrosis

Fibrogenesis is an often-deadly process with increasing world-wide incidence and limited therapeutic options. Pulmonary fibrogenesis involves remodeling of the distal airspace and parenchyma of the lung, and is characterized by excessive extracellular matrix deposition and accumulation of apoptosis-resistant myofibroblasts. Recent studies have added significantly to our understanding of the complex mechanisms involved in lung fibrogenesis. Emerging concepts in this field include the critical role of the epithelium, particularly type II pneumocytes, in the initiation and perpetuation of fibrosis in response to either endogenous or exogenous stress; a growing awareness of alternative activation of macrophages in tissue remodeling; growing appreciation of the alternative origins and phenotypic plasticity of fibroblasts; the roles of epigenetic reprogramming and context-dependent signaling in profibrotic phenotype alterations; and recognition of the importance of cross talk and convergence of intracellular signaling pathways. In vitro, in vivo, and in silico approaches support a paradigm of "disordered re-development" of the lung. Designing effective antifibrotic interventions will require accurate understanding of the complex interactions among the genetic, environmental, epigenetic, biochemical, cellular, and contextual abnormalities that promote pulmonary fibrogenesis.

Loss of steroid receptor co-activator-3 attenuates carbon tetrachloride-induced murine hepatic injury and fibrosis

Hepatic fibrosis, a disease characterized by altered accumulation of extracellular matrix, can cause cirrhosis and liver failure. There is growing interest in the impact of co-activators on hepatic fibrogenesis. Here, we provided genetic evidence that mice lacking steroid receptor co-activator-3 (SRC-3) were protected against carbon tetrachloride (CCl4)-induced acute liver necrosis and chronic hepatic fibrosis. After acute CCl4 treatment, SRC-3(-/-) mice showed attenuated profibrotic response and hepatocyte apoptosis, whereas hepatocyte proliferation was elevated in SRC-3(-/-) mice versus SRC-3+/+ mice. Similarly, chronically CCl4-treated SRC-3(-/-) mice showed significant weakening of inflammatory infiltrates, hepatic stellate cell activation and collagen accumulation in the liver compared with SRC-3+/+ mice. Further investigation revealed that TGFbeta1/Smad signaling pathway was impaired in the absence of SRC-3. Moreover, the expression levels of SRC-3, as assessed in human tissue microarray of liver diseases, correlated positively with degrees of fibrosis. These data revealed that SRC-3(-/-) mice were resistant to CCl4-induced acute and chronic hepatic damage and TGFbeta1/Smad signaling was suppressed in the lack of SRC-3. Our results established an essential involvement of SRC-3 in liver fibrogenesis, which might provide new clues to the future treatment of hepatic fibrosis.

Antifibrotic activity of anisodamine in vivo is associated with changed intrahepatic levels of matrix metalloproteinase-2 and its inhibitor tissue inhibitors of metalloproteinases-2 and transforming growth factor beta1 in rats with carbon tetrachloride-induced liver injury

BACKGROUND AND AIM

To investigate the protective effects and the mechanism of anisodamine on deposition of extracellular matrix in experimental liver fibrosis.

METHODS

Experimental liver fibrosis was produced by carbon tetrachloride (CCL(4)). The preventive group was treated for 10 weeks with anisodamine 7.0 mg/kg per day i.p. injection. Two therapeutic groups were treated for 6 weeks by anisodamine 7.0 or 14.0 mg/kg per day i.p. injection. Studies were made at CCL(4) administration on the 10th weekend. Serum biochemical indices and the contents of malondialdehyde (MDA) and hydroxyproline (HYP) in livers were compared. The expression of transforming growth factor-beta1 (TGF-beta1) was observed by immunohistochemistry. The reverse transcription polymerase chain reaction was used to detect the expressions of matrix metalloproteinase-2 (MMP2) and tissue inhibitor of metalloproteinase-2 (TIMP2) mRNA in livers and the ratio of MMP2 and TIMP2 was measured. The proteins of MMP2 in liver were determined by gelatin zymography.

RESULTS

The serum levels of alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase and hyaluronic acid of liver fibrosis rats improved significantly by treatment with anisodamine. The contents of MDA and HYP in liver decreased and the expressions of TGF-beta1 were inhibited by treatment with anisodamine. The levels of MMP2 and TIMP2 mRNA and the protein of MMP2 in livers were significantly reduced in the anisodamine preventive group and therapeutic groups. The expression ratios of MMP2 and TIMP2 mRNA were adjusted in treated groups.

CONCLUSION

Anisodamine can inhibit hepatic fibrosis.

Hepatic stellate cells express functional CXCR4: role in stromal cell-derived factor-1alpha-mediated stellate cell activation

Chemokine interactions with their receptors have been implicated in hepatic stellate cell (HSC) activation. The hepatic expression of CXCR4 messenger RNA is increased in hepatitis C cirrhotic livers and plasma levels of its endogenous ligand, stromal cell-derived factor-1alpha (SDF-1alpha), correlate with increased fibrosis in these patients. The expression of CXCR4 by HSCs has not been reported. We therefore examined whether HSCs express CXCR4 in vivo and in vitro and explored whether SDF-1alpha/CXCR4 receptor engagement promotes HSC activation, fibrogenesis, and proliferation. The hepatic protein expression of both CXCR4 and SDF-1alpha is increased in hepatitis C cirrhotic livers and immunoflourescent and immunohistochemical staining confirms that HSCs express CXCR4 in vivo. Immortalized human stellate cells as well as primary human HSCs express CXCR4, and cell surface receptor expression increases with progressive culture-induced activation. Treatment of stellate cells with recombinant SDF-1alpha increases expression of alpha-smooth muscle actin and collagen I and stimulates a dose-dependent increase in HSC proliferation. Inhibitor studies suggest that SDF-1alpha/CXCR4-dependent extracellular signal-regulated kinase 1/2 and Akt phosphorylation mediate effects on collagen I expression and stellate cell proliferation.

CONCLUSION

HSCs express CXCR4 receptor in vivo and in vitro. CXCR4 receptor activation by SDF-1alpha is profibrogenic through its effects on HSC activation, fibrogenesis, and proliferation. Extracellular signal-regulated kinase 1/2 and phosphoinositide 3-kinase pathways mediate SDF-1alpha-induced effects on HSC expression of collagen I and proliferation. The availability of small molecule inhibitors of CXCR4 make this receptor an appealing target for antifibrotic approaches.

Involvement of 90-kuD ribosomal S6 kinase in collagen type I expression in rat hepatic fibrosis

AIM: To investigate the relationship between 90-kuD ribosomal S6 kinase (p90RSK) and collagen type I expression during the development of hepatic fibrosis in vivo and in vitro.

METHODS: Rat hepatic fibrosis was induced by intraperitoneal injection of dimethylnitrosamine. The protein expression and cell location of p90RSK and their relationship with collagen type I were determined by co-immunofluoresence and confocal microscopy. Subsequently, RNAi strategy was employed to silence p90RSK mRNA expression in HSC-T6, an activated hepatic stellate cell (HSC) line. The expression of collagen type I in HSC-T6 cells was assessed by Western blotting and real-time polymerase chain reaction. Furthermore, HSCs were transfected with expression vectors or RNAi constructs of p90RSK to increase or decrease the p90RSK expression, then collagen type I promoter activity in the transfected HSCs was examined by reporter assay. Lastly HSC-T6 cells transfected with p90RSK siRNA was treated with or without platelet-derived growth factor (PDGF)-BB at a final concentration of 20 &mgr;g/L and the cell growth was determined by MTS conversion.

RESULTS: In fibrotic liver tissues, p90RSK was over-expressed in activated HSCs and had a significant positive correlation with collagen type I levels. In HSC-T6 cells transfected with RNAi targeted to p90RSK, the expression of collagen type I was down-regulated (61.8% in mRNA, P < 0.01, 89.1% in protein, P < 0.01). However, collagen type I promoter activity was not increased with over-expression of p90RSK and not decreased with low expression either, compared with controls in the same cell line (P = 0.076). Furthermore, p90RSK siRNA exerted the inhibition of HSC proliferation, and also abolished the effect of PDGF on the HSC proliferation.

CONCLUSION: p90RSK is over-expressed in activated HSCs and involved in regulating the abnormal expression of collagen type I through initiating the proliferation of HSCs.

Expression of extracellular matrix genes in cultured hepatic oval cells: an origin of hepatic stellate cells through transforming growth factor beta?

BACKGROUND

Hepatic oval cells, progenitor cells in the liver, can differentiate into hepatocytes and bile duct cells both in vitro and in vivo. Although hepatic stellate cells are another important cell component in the liver, less attention has been focused on the relationship between hepatic oval cells and hepatic stellate cells.

METHODS

Hepatic oval cells were isolated from rats fed a choline-deficient diet supplemented with 0.1% ethionine for 6 weeks and characterized by electron microscopy, flow cytometry, reverse transcription polymerase chain reaction, Western blot and bi-direction differentiation. After treatment with transforming growth factor-beta1 (TGF-beta1), changes in cell viability, morphology, extracellular matrix (ECM) expression and immune phenotype were analysed in these cultured and adherent hepatic oval cells.

RESULTS

The primary cultured hepatic oval cells were positive for the oval cell-specific markers OV-6, BD-1/BD-2 and M2PK as well as the hepatocyte markers albumin and alpha-foetoprotein. These hepatic oval cells differentiated bipotentially into hepatocytes or bile duct-like cells under appropriate conditions. It is noteworthy that these bipotential hepatic oval cells expressed ECM genes stably, including collagens, matrix metalloproteinases and tissue inhibitor of mellatoproteinase. Furthermore, except for growth inhibition and morphological changes in the hepatic oval cells after exposure to TGF-beta1, there was an increased expression of ECM genes, the onset expression of snail and loss expression of E-cadherin. During this process, TGF-beta1 treatment induced an upregulation of marker genes for hepatic stellate cells in hepatic oval cells, such as desmin and GFAP.

CONCLUSION

Except for the expression of ECM, the cultured hepatic oval cells could induce an increased expression of hepatic stellate cell markers by TGF-beta1 through an epithelial-mesenchymal transition process, which might indicate the contribution of hepatic oval cells to liver fibrosis.

Expression of extracellular signal-regulated kinase in hepatic fibrosis and its correlation with collagen type I and III

AIM: To investigate the expression of ERK during the development of hepatic fibrosis and the correlation of ERK and I, III collagens.

METHODS: Hepatic fibrosis was induced by subcutaneous injection of DMN. Rats were killed for study at the end of first, second, third weeks and the clinical operative liver samples were collected. The development expression and location of the ERK in the hepatic tissue and the correlation of ERK with collagen I, III were assessed by means of immunohistochemistry.

RESULTS: The expression of ERK was increased and was closely correlated with that of collagen I and III during the development of rat fibrosis at every time point (1 wk: r = 0.75, 0.68, P < 0.05; 2 wk: r = 0.82, 0.78, P < 0.05; 3 wk: r = 0.74, 0.83, P < 0.05). Similarly, the expression of ERK was enhanced in human fibrotic tissues (1.068 ± 0.258 vs 0.035 ± 0.011, P < 0.05), which was correlated with that of collagen I and III (r = 0.87, 0.88, all P < 0.05).

CONCLUSION: The ERK signal pathway may play an important role in the pathogenesis of hepatic fibrosis.

Rapamycin prevents transforming growth factor-alpha-induced pulmonary fibrosis

Transforming growth factor (TGF)-alpha is a ligand for the epidermal growth factor receptor (EGFR). EGFR activation is associated with fibroproliferative processes in human lung disease and animal models of pulmonary fibrosis. Overexpression of TGF-alpha in transgenic mice causes progressive and severe pulmonary fibrosis; however, the intracellular signaling pathways downstream of EGFR mediating this response are unknown. Using a doxycycline-regulatable transgenic mouse model of lung-specific TGF-alpha expression, we observed increased PCNA protein and phosphorylation of Akt and p70S6K in whole lung homogenates in association with induction of TGF-alpha. Induction in the lung of TGF-alpha caused progressive pulmonary fibrosis over a 7-week period. Daily administration of rapamycin prevented accumulation of total lung collagen, weight loss, and changes in pulmonary mechanics. Treatment of mice with rapamycin 4 weeks after the induction of TGF-alpha prevented additional weight loss, increases in total collagen, and changes in pulmonary mechanics. Rapamycin prevented further increases in established pulmonary fibrosis induced by EGFR activation. This study demonstrates that mammalian target of rapamycin (mTOR) is a major effector of EGFR-induced pulmonary fibrosis, providing support for further studies to determine the role of mTOR in the pathogenesis and treatment of pulmonary fibrosis.

Adenovirus-mediated inhibition of SPARC attenuates liver fibrosis in rats

BACKGROUND

The interaction between fibrogenic cells and extracellular matrix plays a role in liver fibrosis, yet the mechanisms are largely unknown. Secreted protein, acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that is expressed by hepatic stellate cells and is overexpressed in fibrotic livers. We investigated the in vivo role of SPARC in experimentally induced liver fibrosis in rats.

METHODS

A recombinant adenovirus carrying antisense SPARC was constructed (AdasSPARC). Advanced liver fibrosis was induced in Sprague-Dawley rats by prolonged intraperitoneal administration of thioacetamide. Animals received injections of AdasSPARC or Ad beta gal (control adenovirus) via the tail vein and directly into the liver 1 week after the first dose. The pathological changes in liver tissues and indices of fibrosis were assessed at eight weeks. Expression of SPARC, transforming growth factor (TGF)-beta and alpha-smooth muscle actin were evaluated by quantitative real-time polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay and immunohistochemistry.

RESULTS

Hepatic SPARC expression significantly increased during the development of liver fibrosis. AdasSPARC markedly attenuated the development of hepatic fibrosis in rats treated with thiocetamide, as assessed by decreased collagen deposition, lower hepatic content of hydroxyproline and less advanced morphometric stage of fibrosis. AdasSPARC treatment reduced inflammatory activity (Knodell score) and suppressed transdifferentiation of hepatic stellate cell to the myofibroblasts like phenotype in vivo. Furthermore, in vitro inhibition of SPARC on hepatic stellate cells decreases the production of TGF-beta.

CONCLUSIONS

This is the first study to demonstrate that knockdown of hepatic SPARC expression ameliorates thioacetamide-induced liver fibrosis in rats with chronic liver injury. SPARC is a potential target for gene therapy in liver fibrosis.

The tumor suppressor protein PTEN inhibits rat hepatic stellate cell activation

BACKGROUND

Following a fibrogenic stimulus, the hepatic stellate cell (HSC) transforms from a quiescent to an activated cell type associated with increased proliferation, collagen and smooth muscle alpha-actin (alphaSMA) expression. Phosphatase and Tensin Homolog Deleted on Chromosome Ten (PTEN), a tumor suppressor phosphatase, has been shown to play a role in several nonmalignant diseases. Here, we investigated the role of PTEN during HSC activation.

METHODS

Rat HSCs 2 days after isolation were transduced with adenoviruses expressing either the wild-type (WT) or a dominant negative form of PTEN, and culture-associated activation of HSCs, including morphological changes, expression of alphaSMA and alpha1(I) collagen, and cell proliferation, were evaluated. Apoptosis of HSCs was detected by measuring activity of caspase 3/7. Phosphorylation status of Akt, p70(S6K), and Erk was detected by Western blotting.

RESULTS

Overexpression of WT-PTEN inhibited phenotypic changes were associated with HSC activation, including morphological changes, expression of alphaSMA and alpha1(I) collagen, and HSC proliferation, including cyclin D1 expression. WT-PTEN expression also induced apoptosis in HSCs with increased caspase 3/7 activity. Expression of WT-PTEN also caused decreased activation of Akt, p70(S6K), and Erk signaling pathways.

CONCLUSIONS

Taken together, these findings show that PTEN represents an important negative regulator for transactivation of HSCs. This may have important implications for the design of therapeutic strategies to prevent the progression of liver fibrosis.

Liver cell-derived microparticles activate hedgehog signaling and alter gene expression in hepatic endothelial cells

BACKGROUND & AIMS

Angiogenesis contributes to vascular remodeling during cirrhosis. In cirrhotic livers, cholangiocytes, and myofibroblastic hepatic stellate cells (MF-HSC) produce Hedgehog (Hh) ligands. During embryogenesis Hh ligands are released from ligand-producing cells in microparticles and activate Hh signaling in endothelial cells. We studied whether adult liver cell-derived microparticles contain Hh ligands that alter hepatic sinusoidal endothelial cells (SEC).

METHODS

MF-HSC and cholangiocytes were exposed to platelet-derived growth factor to induce Hh ligands; microparticles were isolated from medium, analyzed by transmission electron microscopy and immunoblots, and applied to Hh-reporter-containing cells. Microparticles were obtained from serum and bile of rats after bile duct ligation (BDL) or sham surgery and applied to normal primary liver SEC with or without cyclopamine, an Hh signaling inhibitor. Effects on SEC gene expression were evaluated by quantitative reverse-transcription polymerase chain reaction and immunoblotting. Hh target gene expression and SEC activation markers were compared in primary SEC and in liver sections from healthy and BDL rats.

RESULTS

Platelet-derived growth factor-treated MF-HSC and cholangiocytes released exosome-enriched microparticles containing biologically-active Hh ligands. BDL increased release of Hh-containing exosome-enriched microparticles into plasma and bile. Transmission electron microscopy and immunoblots revealed similarities among microparticles from all sources; all microparticles induced similar Hh-dependent changes in SEC gene expression. SEC from healthy livers did not express Hh target genes or activation markers, but both were up-regulated in SEC after BDL.

CONCLUSIONS

Hh-containing exosome-enriched microparticles released from liver cells alter hepatic SEC gene expression, suggesting a novel mechanism for cirrhotic vasculopathy.

Platelets contribute to the reduction of liver fibrosis in mice

BACKGROUND AND AIM

Several recent studies have reported that liver cirrhosis (LC) can be ameliorated, but few adequate strategies are available against liver fibrosis. Although LC clinically shows thrombocytopenia and hypersplenism, the correlation with liver fibrosis and platelets remains unclear. The aim of the present study was to investigate the effect of platelets on liver fibrosis in mouse models.

METHODS

To induce liver fibrosis, C57BL6 female mice were injected i.p. with 1 mL/kg carbon tetrachloride (CCl(4)) twice a week for 8 weeks. Thrombocytosis was achieved by giving thrombopoietin or splenectomy in addition to CCl(4) intoxication. At 8 weeks, whole blood and liver specimens were obtained for studies as follows: peripheral platelet counts, histopathological examination, hydroxyproline assay, immunostaining, quantification of mRNA expression, and microarray analysis.

RESULTS

Thrombocytosis significantly reduced liver fibrosis and hydroxyproline content of liver tissues compared to mice with CCl(4) administration alone. Platelets suppressed increments in mRNA expression for transforming growth factor-beta, and increased matrix metalloproteinase-9 expression in the liver. Microarray analysis of the liver revealed that platelets upregulated gene expressions involved in cell proliferation compared to expression in mice with CCl(4) intoxication alone. Platelets also increased liver volume, proliferative cell nuclear antigen labeling index, and mitotic index in fibrotic mice.

CONCLUSION

These results clearly show that platelets reduce liver fibrosis and promote liver regeneration, even under cirrhotic conditions. We, therefore, propose that platelets could offer a potent tool in the treatment of liver cirrhosis.

Role of angiotens Ⅱ in pathogenesis of alcoholic liver fibrosis in rats

AIM: To determine role of angiotensin Ⅱ (AngⅡ) in alcoholic liver fibrosis and to provide a new suitable agent for clinical treatment.

METHODS: Wistar male rats were randomly divided into 3 groups: control group (n = 30), experimental group (n = 50) which were intragastricaly infused with NS or alcohol, and Captopril group (n = 30) treated with captopril twice a day for 12w [8 g/(kg·d)] following two weeks' of alcohol infusion. HE and van Giesion staining were used to observe the histological changes, and serum or hepatic hyaluronic acid, laminin and angiotensin Ⅱ were detected using radioimmunoassay method. Immunohistochemistry staining was used to detect the expressions of type Ⅰ and type Ⅳ collagen in liver.

RESULTS: The serum AngⅡ level began to increase after eight weeks' of ethanol feeding in alcohol-fed rats and reached the highest level at the end of 12 weeks, significantly higher than controls (1250.50 ± 170.06 vs 598.20 ± 83.73, P < 0.0005). AngⅡ, detected in liver, progressing increased and showed significant difference between alcohol-fed rats and controls (1083.4 ± 197.45 vs 568.2 ± 89.82, 1382.5 ± 154.88 vs 570.2 ± 77.63, 1504.00 ± 173.12 vs 579.2 ± 87.65, all P < 0.0005). HE and van Giesion staining showed no degeneration or necrosis or inflammatory cell infiltration or fibroproliferation in captopril-treated rats, whereas dramatic changes were observed in alcohol-fed rats. At the end of week 12, serum hepatic hyaluronic acid and laminin level were significantly increased in alcohol-fed rats than either the controls or the captopril-treated rats (33.9 ± 2.77 vs 22.0 ± 2.31, 24.2 ± 1.9; 72.5 ± 3.31 vs 54.4 ± 3.15, 56.7 ± 3.22, all P < 0.05). The result of immunohistochemistry staining showed no different location of positive staining, but the strength and areas of type Ⅰ or type Ⅳ collagen-positive staining were significantly lower in captopril-treated rats than in alcohol-fed rats (6.45 ± 0.41, 7.01 ± 0.49 vs 17.23 ± 0.62, 18.04 ± 0.89, all P < 0.0005).

CONCLUSION: AngⅡ is increased both in plasma and also in liver tissue. Captopril inhibits formation of liver fibrosis, decreases the plasma level of HA and LN and reduces the expression of collagen type Ⅰ and Ⅳ in liver. Thus AngⅡ promotes the alcohol-induced liver fibrosis.

Disease-specific mechanisms of fibrosis: hepatitis C virus and nonalcoholic steatohepatitis

Our mechanistic understanding of liver fibrosis has increased dramatically in recent years for all liver diseases and for hepatitis C and nonalcoholic steatohepatitis (NASH) in particular. Hepatitis C causes liver injury and fibrosis through direct cytopathic means, direct and indirect interactions with hepatic stellate cells, and activation of the immune system. Steatosis and insulin resistance, which are intrinsic deficits in NASH, are also of great importance in hepatitis C and may be induced by viral or host metabolic factors. For NASH, the key mediators of damage include oxidative stress, fat compartmentalization, visceral fat, apoptosis, and adipokine derangement. This article explores in depth the disease-specific mechanisms of fibrosis in hepatitis C and NASH, with a focus on recent developments.

NIM811 (N-methyl-4-isoleucine cyclosporine), a mitochondrial permeability transition inhibitor, attenuates cholestatic liver injury but not fibrosis in mice

Cholestasis causes hepatocyte death, possibly because of mitochondrial injury. This study investigated whether NIM811 (N-methyl-4-isoleucine cyclosporine), an inhibitor of the mitochondrial permeability transition (MPT), attenuates cholestatic liver injury in vivo. Cholestasis was induced in mice by bile duct ligation (BDL). NIM811 was gavaged (20 mg/kg) before BDL and daily (10 mg/kg) afterward. Mitochondrial depolarization, cell death, and MPT onset were assessed by intravital confocal/multiphoton microscopy of rhodamine 123, propidium iodide, and calcein. After BDL, serum alanine aminotransferase (ALT), hepatic necrosis, and apoptosis all increased. NIM811 decreased ALT, necrosis, and apoptosis by 60 to 86%. In vehicle-treated mice at 6 h after BDL, viable hepatocytes with depolarized mitochondria were 18/high-power field (hpf), and nonviable cells were approximately 1/hpf, showing that depolarization preceded necrosis. Calcein entered mitochondria after BDL, indicating MPT onset in vivo. NIM811 decreased depolarization by 72%, prevented calcein entry into mitochondria, and blocked release of cytochrome c. Hepatic tumor necrosis factor alpha, transforming growth factor-beta1, procollagen alpha1(I) mRNA, alpha-smooth muscle actin, and Sirius red staining for collagen increased after BDL but were not different in vehicle- and NIM811-treated mice. Taken together, NIM811 decreased cholestatic necrosis and apoptosis but did not block fibrosis, indicating that the MPT plays an important role in cholestatic cell death in vivo.

[Bushen Rougan Recipe in prevention of hepatic fibrosis in rats induced by dimethylnitrosamine: a study on its preliminary mechanism]

OBJECTIVE

To study the effects of Bushen Rougan Recipe (BSRGR), a compound traditional Chinese herbal medicine, on hepatic fibrosis in rats induced by dimethylnitrosamine (DMN), and to explore its preliminary mechanism.

METHODS

A total of 40 male Wistar rats were randomly divided into normal control group (n=10), untreated group (n=15), and BSRGR group (n=15). Except for the rats in normal control group, hepatic fibrosis in rats was induced by peritoneal injection of DMN for 4 weeks. And the rats in the BSRGR group were also intragastrically administered BSRGR within the 4-week course. At the end of the 4-week course, rats were all sacrificed. The liver functions were determined by automatic biochemistry analyzer, including serum total bilirubin (Tbil), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and albumin. Expressions of connective tissue growth factor (CTGF) and collagen type I mRNA in liver tissue were detected by reverse transcription polymerase chain reaction.

RESULTS

It was found that the serum Tbil level and the activities of AST, ALT were declined in the BSRGR group as compared with those in the untreated group (P<0.01). The serum albumin content in the BSRGR group was increased as compared with that in the untreated group (P<0.01). The expressions of collagen type I and CTGF mRNAs in the untreated group were higher than those in the BSRGR group (P<0.01).

CONCLUSION

BSRGR can decrease the expressions of collagen type I and CTGF mRNAs in the rats with hepatic fibrosis, which may be one of possible mechanisms in treating hepatic fibrosis.

Phosphatidylinositol 3-kinase/Akt pathway regulates hepatic stellate cell apoptosis

AIM: To investigate the role of phosphatidylinositol 3-kinase (PI 3-K)/Akt signaling pathway in the balance of HSC activation and apoptosis in rat hepatic stellate cells (HSC).

METHODS: An activated HSC cell line was used in this study. LY 294002, the PI 3-K/Akt signal pathway blocker was used to investigate the molecular events on apoptosis in HSC and to interpret the role of this pathway in HSC apoptosis. Immunocytochemistry, Western blot and reverse transcription polymerase chain reaction (RT-PCR) analysis were applied to detect the expression of PI 3-K, and simultaneously phosphorylated-Akt (p-Akt) and total-Akt were determined by Western blot. The HSC apoptosis was examined by annexin-V/propidium iodide double-labelled flow cytometry and transmission electron microscopy.

RESULTS: The apoptosis rates in LY 294002 (30.82% ± 2.90%) and LY 294002 + PDGF-BB (28.16% ± 2.58%) groups were significantly increased compared with those of control (9.02% ± 1.81%) and PDGF-BB (4.35% ± 1.18%). PDGF-BB augmented PI 3-K and p-Akt expression. LY 294002 significantly reduced the contents of PI 3-K and p-Akt. mRNA transcription evaluated by RT-PCR showed similar tendencies as protein expression.

CONCLUSION: Inhibition of PI 3-K/Akt signaling pathway induces apoptosis in HSC.

Noninvasive monitoring of hepatitis C fibrosis progression

Noninvasive approaches in the diagnosis and monitoring of fibrosis are still evolving. Transient elastography is an inexpensive, rapid, and relatively accurate form of noninvasive monitoring, especially in severe fibrosis It is a nascent technology, however, and there is no clear indication that elastography is better than biopsy for less severe fibrosis. With improved resolution and longer term data, it may become a vital supplement. The combined use of transient elastography and biochemical markers seems to be the most promising noninvasive technique.

Emphasis on prevention and treatment of hepatic fibrosis

Hepatic fibrosis is a common pathological basis of chronic liver disease and liver cirrhosis. HBV infection is highly prevalent in China and there is an increasing trend of liver disease caused by HCV and other factors. However, no specific virus-eradicating drugs have been available for liver diseases caused by HBV and HCV. Cytokine-triggered and HSC-triggered waterfall effect does not cease with removal of the original pathogenic factor. Therefore, we should raise the awareness of prevention and treatment of hepatic fibrosis and gradually develop a set of basic countermeasures against hepatic fibrosis and standardize its implementation. This paper highlighted some misunderstandings in current prevention and treatment of hepatic fibrosis, and pointed out the necessity and urgency of prevention and treatment of liver fibrosis.

Construction of COL1A1-shRNA expression plasmid and screening of effective sequences to inhibit COL1A1 expression

AIM: To construct and select procollagen type 1 alpha 1 (COL1A1) short hairpin RNA (shRNA) expression plasmid that can inhibit COL1A1 mRNA expression in rat hepatic stellate cell (HSC).

METHODS: Rat COL1A1 cDNA sequence was obtained from NCBI website. Three small interfering RNA sequences were selected through online design of the Whitehead Institute. The corresponding double-stranded DNA was used to construct pGPU6/GFP/Neo plasmids, namely pGPU6/GFP/Neo-shRNA-A, pGPU6/GFP/Neo-shRNA-B and pGPU6/GFP/Neo-shRNA-C. HSC-T6 cells were transfected with a green fluorescent protein (GFP)-labeled siRNA to assess the transfection efficiency. To get most effective and optimal dosage siRNA, the three plasmids (1, 2, 3, 4 μg) were transfected into HSC-T6 cells with Lipofectamine 2000 respectively, and the untreated HSC-T6 cells were used as controls. The expression of COL1A1 mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR) after the most effective and optimal dosage was used.

RESULTS: The expression plasmids targeting on COL1A1 mRNA were successfully constructed, and confirmed by agarose electrophoresis and sequence analysis. The transfection efficiencies at a dose of 1, 2, 3, and 4 μg were approximately 16.7%, 20.3%, 23.5%, and 22.3%, and 2 μg was considered as the most optimal dosage in each group. The inhibitory rates of COL1A1 mRNA levels in the HSC-T6 cells transfected with pGPU6/GFP/Neo-shRNA-A, pGPU6/GFP/Neo-shRNA-B, and pGPU6/GFP/Neo-shRNA-C were 16.6%, 63.3%, and 80.3%, respectively, when 2 μg siRNA plasmid was used.

CONCLUSION: The constructed expression plasmid pGPU6/GFP/Neo-shRNA-C can effectively inhibit the expression of COL1A1 mRNA, providing a new method and material for the treatment of liver fibrosis.

Rosiglitazone prevents murine hepatic fibrosis induced by Schistosoma japonicum

AIM: To evaluate the effect of rosiglitazone in a murine model of liver fibrosis induced by Schistosoma japonicum infection.

METHODS: A total of 50 mice were randomly and averagely divided into groups A, B, C, D and E. The mice in group A served as normal controls, while those in the other four groups were infected with Schistosoma japonicum to induce the model of liver fibrosis. Besides, the mice in groups C, D and E were treated with praziquantel, rosiglitazone and praziquantel plus rosiglitazone, respectively. NF-κB binding activity and expression of PPARγ-mRNA were determined by Western blot assay and real-time quantitative PCR. Radioimmunoassay technique was used to detect the serum content changes of TNF-α and IL-6. Histological specimens were stained with HE. Expression of TGF-β1, a-smooth muscle actin and type I and type III collagen was detected by immunohistochemistry and multimedia color pathographic analysis system.

RESULTS: Inflammation and fibrosis in the rosiglitazone plus praziquantel treatment group (group E) were lightest among the mice infected with Schistosoma (P < 0.05). To further explore the mechanism of rosiglitazone action, we found that rosiglitazone can significantly increase the expression of PPARγ [E: -18.212 ± (-3.909) vs B: -27.315 ± (-6.348) and C: -25.647 ± (-5.694), P < 0.05], reduce the NF-κB binding activity (E: 88.89 ± 19.34 vs B: 141.11 ± 15.37, C: 112.89 ± 20.17 and D: 108.89 ± 20.47, P < 0.05), and lower the serum level of TNF-α (E: 1.613 ± 0.420 ng/mL vs B: 2.892 ± 0.587 ng/mL, C: 2.346 ± 0.371 ng/mL and D: 2.160 ± 0.395 ng/mL, P < 0.05) and IL-6 (E: 0.106 ± 0.021 ng/mL vs B: 0.140 ± 0.031 ng/mL and C: 0.137 ± 0.027 ng/mL, P < 0.05) in mice with liver fibrosis. Rosiglitazone can also substantially reduce the hepatic expression of TGF-β1, α-SMA type I and type III collagen in mice with liver fibrosis.

CONCLUSION: The activation of PPARγ by its ligand can retard liver fibrosis and suggest the use of rosiglitazone for the treatment of liver fibrosis due to Schistosoma japonicum infection.

Down-regulation of transforming growth factor β1/activin receptor-like kinase 1 pathway gene expression by herbal compound 861 is related to deactivation of LX-2 cells

AIM: To investigate the effect of herbal compound 861 (Cpd861) on the transforming growth factor-β1 (TGFβ1)/activin receptor-like kinase 1 (ALK1, type I receptor) signaling-pathway-related gene expression in the LX-2 cell line, and the inhibitory mechanism of Cpd861 on the activation of LX-2 cells.

METHODS: LX-2 cells were treated with TGFβ1 (5 ng/mL) Cpd861 (0.1 mg/mL), TGFβ1 (5 ng/mL) plus Cpd861 (5 ng/mL) for 24 h to investigate the effect of Cpd861 on the TGFβ1/ALK1 pathway. Real-time PCR was performed to examine the expression of α-SMA (α-smooth muscle actin), ALK1, Id1 (inhibitor of differentiation 1). Western blotting was carried out to measure the levels of α-SMA and phosphorylated Smad1, and immunocytochemical analysis for the expression of α-SMA.

RESULTS: In LX-2 cells, TGFβ1/ALK1-pathway-related gene expression could be stimulated by TGFβ1, which led to excessive activation of the cells. Cpd861 decreased the activation of LX-2 cells by reducing the expression of α-SMA mRNA and protein expression. This effect was related to inhibition of the above TGFβ1/ALK1-pathway-related expression of genes such as Id1 and ALK1, and phosphorylation of Smad1 in LX-2 cells, even with TGFβ1 co-treatment for 24 h.

CONCLUSION: Cpd861 can restrain the activation of LX-2 cells by inhibiting the TGFβ1/ALK1/Smad1 pathway.

Effect of Oxymatrine on the TGFbeta-Smad signaling pathway in rats with CCl4-induced hepatic fibrosis

AIM: To explore the anti-fibrotic effect of Oxymatrine on CCl₄-induced liver fibrosis in rats and its modulation on the TGFbeta-Smad signaling pathway.

METHODS: One hundred healthy male SD rats were randomly divided into three groups: normal group (n = 20), treatment group of Oxymatrine (n = 40) and CCl₄-induced fibrosis group (n = 40). Experimental hepatic fibrosis was induced by subcutaneous injection of carbon tetrachloride (CCl₄ soluted in liquid paraffin with the concentration of 300 g/L, the dosage of injection was 3 mL/kg, twice per week for 8 wk). The treated rats received Oxymatrine via celiac injection at a dosage of 10 mg/kg twice a week at the same time. The deposition of collagen was observed with H&E and Masson staining. The concentration of serum TGF-β1 was assayed with ELISA. The gene expression of Smads and CBP (CREB binding protein) was detected with in situ hybridization (ISH) and immunohistochemistry (IH), respectively. All the experimental figures were scanned and analyzed with special figure-analysis software.

RESULTS: A significant reduction of collagen deposition and rearrangement of the parenchyma was noted in the liver tissue of Oxymatrine-treated rats. The semi-quantitative histological scores (2.43 ± 0.47 &mgr;m²vs 3.76 ± 0.68 &mgr;m², P < 0.05) and average area of collagen in those rats were significantly decreased when compared with hepatic cirrhosis model rats (94.41 ± 37.26 &mgr;m²vs 290.86 ± 89.37 &mgr;m², P < 0.05). The gene expression of Smad 3 mRNA was considerably decreased in the treated animals. The A value of Smad 3 mRNA was lower in the treated rats than the model rats (0.034 ± 0.090 vs 0.167 ± 0.092, P < 0.05). Contrarily, the A value of Smad 7 mRNA was increased considerably in the treated animals (0.175 ± 0.065 vs 0.074 ± 0.012, P < 0.05). There was an obvious decrease in the expression of CBP mRNA in treated rats as illuminated by a reduction of its A value when compared with model rats (0.065 ± 0.049 vs 0.235 ± 0.025, P < 0.001).

CONCLUSION: Oxymatrine is effective in reducing the production and deposition of collagen in the liver tissue of experimental rats. Oxymatrine could promote the expression of Smad 7 and inhibit the expression of Smad 3 and CBP in CCl₄-induced hepatic fibrosis in SD rats, could modulate the fibrogenic signal transduction of TGFβ-Smad pathway.

Cellular and molecular mechanisms of fibrosis

Fibrosis is defined by the overgrowth, hardening, and/or scarring of various tissues and is attributed to excess deposition of extracellular matrix components including collagen. Fibrosis is the end result of chronic inflammatory reactions induced by a variety of stimuli including persistent infections, autoimmune reactions, allergic responses, chemical insults, radiation, and tissue injury. Although current treatments for fibrotic diseases such as idiopathic pulmonary fibrosis, liver cirrhosis, systemic sclerosis, progressive kidney disease, and cardiovascular fibrosis typically target the inflammatory response, there is accumulating evidence that the mechanisms driving fibrogenesis are distinct from those regulating inflammation. In fact, some studies have suggested that ongoing inflammation is needed to reverse established and progressive fibrosis. The key cellular mediator of fibrosis is the myofibroblast, which when activated serves as the primary collagen-producing cell. Myofibroblasts are generated from a variety of sources including resident mesenchymal cells, epithelial and endothelial cells in processes termed epithelial/endothelial-mesenchymal (EMT/EndMT) transition, as well as from circulating fibroblast-like cells called fibrocytes that are derived from bone-marrow stem cells. Myofibroblasts are activated by a variety of mechanisms, including paracrine signals derived from lymphocytes and macrophages, autocrine factors secreted by myofibroblasts, and pathogen-associated molecular patterns (PAMPS) produced by pathogenic organisms that interact with pattern recognition receptors (i.e. TLRs) on fibroblasts. Cytokines (IL-13, IL-21, TGF-beta1), chemokines (MCP-1, MIP-1beta), angiogenic factors (VEGF), growth factors (PDGF), peroxisome proliferator-activated receptors (PPARs), acute phase proteins (SAP), caspases, and components of the renin-angiotensin-aldosterone system (ANG II) have been identified as important regulators of fibrosis and are being investigated as potential targets of antifibrotic drugs. This review explores our current understanding of the cellular and molecular mechanisms of fibrogenesis.

Multiple effects of acetaminophen and p38 inhibitors: towards pathway toxicology

The majority of drug-related toxicities are idiosyncratic, with little pathophysiological insight and mechanistic understanding. Pathway toxicology is an emerging field of toxicology in the post-genomic era that studies the molecular interactions between toxicants and biological pathways as a way to bridge this knowledge gap. Using two case studies--acetaminophen and p38 MAPK inhibitors--this review illustrates how a pathway-based perspective has advanced our understanding of compound and target-based toxicities. The advancement of pathway toxicology will be dependent on integrated applications of techniques from basic sciences and a fundamental understanding of the interdependence of multiple biological pathways in living organisms.

Gene therapy for hepatic fibrosis

Hepatic fibrosis is a common pathological process of chronic liver diseases, characterized by increased synthesis and relatively low degradation of extracellular matrix (ECM) resulting from their dynamic imbalance. Recent progress in molecular biology techniques has made it possible to treat hepatic fibrosis with gene therapy. At present, the commonly used method is to induce the expression of exogenous genes by transducing enough therapeutic genes into injured liver to delay or cure liver fibrosis.