Role of transforming growth factor beta type II receptor in hepatic fibrosis: studies of human chronic hepatitis C and experimental fibrosis in rats

Using quantitative immunohistochemistry in patients at high risk for hepatocellular cancer

Hepatocellular carcinoma (HCC) is the primary form of liver cancer and a major cause of cancer death worldwide. Early detection is key to effective treatment. Yet, early diagnosis is challenging, especially in patients with cirrhosis, who are at high risk of developing HCC. Dysfunction or loss of function of the transforming growth factor β (TGF-β) pathway is associated with HCC. Here, using quantitative immunohistochemistry analysis of samples from a multi-institutional repository, we evaluated if differences in TGF-β receptor abundance were present in tissue from patients with only cirrhosis compared with those with HCC in the context of cirrhosis. We determined that TGFBR2, not TGFBR1, was significantly reduced in HCC tissue compared with cirrhotic tissue. We developed an artificial intelligence (AI)-based process that correctly identified cirrhotic and HCC tissue and confirmed the significant reduction in TGFBR2 in HCC tissue compared with cirrhotic tissue. Thus, we propose that a reduction in TGFBR2 abundance represents a useful biomarker for detecting HCC in the context of cirrhosis and that incorporating this biomarker into an AI-based automated imaging pipeline could reduce variability in diagnosing HCC from biopsy tissue.

Green Synthesis of Silymarin-Chitosan Nanoparticles as a New Nano Formulation with Enhanced Anti-Fibrotic Effects against Liver Fibrosis

Background: Silymarin (SIL) has long been utilized to treat a variety of liver illnesses, but due to its poor water solubility and low membrane permeability, it has a low oral bioavailability, limiting its therapeutic potential. Aim: Design and evaluate hepatic-targeted delivery of safe biocompatible formulated SIL-loaded chitosan nanoparticles (SCNPs) to enhance SIL’s anti-fibrotic effectiveness in rats with CCl₄-induced liver fibrosis. Methods: The SCNPs and chitosan nanoparticles (CNPs) were prepared by ionotropic gelation technique and are characterized by physicochemical parameters such as particle size, morphology, zeta potential, and in vitro release studies. The therapeutic efficacy of successfully formulated SCNPs and CNPs were subjected to in vivo evaluation studies. Rats were daily administered SIL, SCNPs, and CNPs orally for 30 days. Results: The in vivo study revealed that the synthesized SCNPs demonstrated a significant antifibrotic therapeutic action against CCl₄-induced hepatic injury in rats when compared to treated groups of SIL and CNPs. SCNP-treated rats had a healthy body weight, with normal values for liver weight and liver index, as well as significant improvements in liver functions, inflammatory indicators, antioxidant pathway activation, and lipid peroxidation reduction. The antifibrotic activities of SCNPs were mediated by suppressing the expression of the main fibrosis mediators TGFβR1, COL3A1, and TGFβR2 by boosting the hepatic expression of protective miRNAs; miR-22, miR-29c, and miR-219a, respectively. The anti-fibrotic effects of SCNPs were supported by histopathology and immunohistochemistry (IHC) study. Conclusions: According to the above results, SCNPs might be the best suitable carrier to target liver cells in the treatment of liver fibrosis.

Preparation and Characterization of Silymarin-Conjugated Gold Nanoparticles with Enhanced Anti-Fibrotic Therapeutic Effects against Hepatic Fibrosis in Rats: Role of MicroRNAs as Molecular Targets

BACKGROUND

The main obstacles of silymarin (SIL) application in liver diseases are its low bioavailability, elevated metabolism, rapid excretion in bile and urine, and inefficient intestinal resorption. The study aimed to synthesize and characterize silymarin-conjugated gold nanoparticles (SGNPs) formulation to improve SIL bioavailability and release for potentiating its antifibrotic action.

METHODS

Both SGNPs and gold nanoparticles (GNPs) were prepared and characterized using standard characterization techniques. The improved formulation was assessed for in vitro drug release study and in vivo study on rats using CCl₄ induced hepatic fibrosis model. SIL, SGNPs, and GNPs were administered by oral gavage daily for 30 days. At the end of the study, rats underwent anesthesia and were sacrificed, serum samples were collected for biochemical analysis. Liver tissues were collected to measure the genes and microRNAs (miRNAs) expressions. Also, histopathological and immunohistochemistry (IHC) examinations of hepatic tissues supported these results.

RESULTS

The successful formation and conjugation of SGNPs were confirmed by measurements methods. The synthesized nanohybrid SGNPs showed significant antifibrotic therapeutic action against CCl₄-induced hepatic damage in rats, and preserved normal body weight, liver weight, liver index values, retained normal hepatic functions, lowered inflammatory markers, declined lipid peroxidation, and activated the antioxidant pathway nuclear factor erythroid-2-related factor 2 (NRF2). The antifibrotic activities of SGNPs mediated through enhancing the hepatic expression of the protective miRNAs; miR-22, miR-29c, and miR-219a which results in suppressed expression of the main fibrosis mediators; TGFβR1, COL3A1, and TGFβR2, respectively. The histopathology and IHC analysis confirmed the anti-fibrotic effects of SGNPs.

CONCLUSIONS

The successful synthesis of SGNPs with sizes ranging from 16 up to 20 nm and entrapment efficiency and loading capacity 96% and 38.69%, respectively. In vivo studies revealed that the obtained nano-formulation of SIL boosted its anti-fibrotic effects.

TGF-β signaling: A recap of SMAD-independent and SMAD-dependent pathways

Transforming growth factor-β (TGF-β) is a proinflammatory cytokine known to control a diverse array of pathological and physiological conditions during normal development and tumorigenesis. TGF-β-mediated physiological effects are heterogeneous and vary among different types of cells and environmental conditions. TGF-β serves as an antiproliferative agent and inhibits tumor development during primary stages of tumor progression; however, during the later stages, it encourages tumor development and mediates metastatic progression and chemoresistance. The fundamental elements of TGF-β signaling have been divulged more than a decade ago; however, the process by which the signals are relayed from cell surface to nucleus is very complex with additional layers added in tumor cell niches. Although the intricate understanding of TGF-β-mediated signaling pathways and their regulation are still evolving, we tried to make an attempt to summarize the TGF-β-mediated SMAD-dependent andSMAD-independent pathways. This manuscript emphasizes the functions of TGF-β as a metastatic promoter and tumor suppressor during the later and initial phases of tumor progression respectively.

Adipocyte Fatty Acid Binding Protein Promotes the Onset and Progression of Liver Fibrosis via Mediating the Crosstalk between Liver Sinusoidal Endothelial Cells and Hepatic Stellate Cells

Development of liver fibrosis results in drastic changes in the liver microenvironment, which in turn accelerates disease progression. Although the pathological function of various hepatic cells in fibrogenesis is identified, the crosstalk between them remains obscure. The present study demonstrates that hepatic expression of adipocyte fatty acid binding protein (A-FABP) is induced especially in the liver sinusoidal endothelial cells (LSECs) in mice after bile duct ligation (BDL). Genetic ablation and pharmacological inhibition of A-FABP attenuate BDL- or carbon tetrachloride-induced liver fibrosis in mice associating with reduced collagen accumulation, LSEC capillarization, and hepatic stellate cell (HSC) activation. Mechanistically, elevated A-FABP promotes LSEC capillarization by activating Hedgehog signaling, thus impairs the gatekeeper function of LSEC on HSC activation. LSEC-derived A-FABP also acts on HSCs in paracrine manner to potentiate the transactivation of transforming growth factor β1 (TGFβ1) by activating c-Jun N-terminal kinase (JNK)/c-Jun signaling. Elevated TGFβ1 subsequently exaggerates liver fibrosis. These findings uncover a novel pathological mechanism of liver fibrosis in which LSEC-derived A-FABP is a key regulator modulating the onset and progression of the disease. Targeting A-FABP may represent a potential approach against liver fibrosis.

Hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP) confers protection against hepatic fibrosis through downregulation of transforming growth factor β receptor II

Hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP) has antimicrobial, antioxidant, anti-inflammatory, mitogenic, and antiapoptotic effects and thus exerts important functions in the maintenance of integrity and homeostasis of several organs, such as the gastrointestinal tract, pancreas, and liver. Although the potent hepatoprotective effect of HIP/PAP has been validated, its impact on liver fibrosis has not been reported. In this study, we evaluated the role of HIP/PAP on hepatic fibrosis and explored the possible underlying mechanisms. We found that the expression of HIP/PAP and its mouse counterpart, Reg3B, was markedly upregulated in fibrotic human or mouse livers. Intraperitoneal (i.p.) interleukin (IL)-10, IL-6, and TNF-α but not TGF-β1 significantly induced hepatic overexpression of Reg3B in mice. In both CCl₄ and BDL liver fibrosis models, adenovirus-mediated ectopic expression of HIP/PAP markedly alleviated liver injury, inflammation, collagen deposition, hepatic stellate cell activation, and the overexpression of profibrotic cytokines, including transforming growth factor β1 (TGF-β1), platelet-derived growth factor (PDGF)-A, B, connective tissue growth factor (CTGF), and plasminogen activator inhibitor-1 (PAI-1), in mice. In vitro experiments demonstrated that, in addition to suppressing hepatic stellate cell proliferation and accelerating hepatocyte proliferation, HIP/PAP mitigated TGF-β1-induced hepatic stellate cell activation, hepatocyte epithelial-mesenchymal transition (EMT) and upregulated expression of profibrotic cytokines in both hepatic stellate cells and hepatocytes. Moreover, HIP/PAP attenuated the overexpression of TGF-β receptor II (TGF-βRII) in fibrotic mouse livers and decreased the basal expression of TGF-βRII in nonfibrotic mouse livers as well as in cultured hepatocytes and hepatic stellate cells, which is at least partly attributable to the TGF-β1-antagonizing function of HIP/PAP. This study indicates that increased expression of hepatic HIP/PAP serves as a countermeasure against liver injury and fibrosis. Exogenous supplementation of HIP/PAP might be a promising therapeutic agent for hepatic fibrosis as well as liver injury.

TGF-β1 serum concentrations and receptor expressions in the lens capsular of dogs with diabetes mellitus

Tissue fibrosis as complication of diabetes mellitus is known in humans. Because TGF-β1induces fibrosis and is elevated in humans suffering from diabetes mellitus we measured this growth factor in serum of dogs with diabetes mellitus and compared it with healthy dogs and those with fibrotic diseases. Further we measured the expression of TGF-β1receptor on lens capsule to investigate possible association between diabetes mellitus and cataract associated alterations. TGF-β1 was measured in serum of 12 dogs with diabetes mellitus, 20 healthy controls and 12 dogs with fibrotic diseases. Dogs with diabetes mellitus and fibrotic diseases have significantly increased TGF-β1 serum concentrations compared to healthy controls. Some dogs with diabetes mellitus showed increased expression of TGF-β1 receptor in lens capsule. Based on our observations we can conclude that TGF-β1 elevation in dogs with diabetes mellitus may induces complications of the disease and may participates on lens alteration.

Effect of intravenous injection of recombinant IL-10 gene vector on expression of TNF-α, PDGF-β and COX-2 in experimental fibrosis in rats

AIM: To study the effect of intravenous injection of recombinant IL-10 (rIL-10) gene vector on the expression of tumor necrosis factor-α (TNF-α), platelet derivative growth factor-β (PDGF-β) and cyclooxygenase-2 (COX-2) in pig serum-induced experimental liver fibrosis in rats.

METHODS: Thirty SD rats were divided into a normal control and a fibrosis model group. The normal control group was intraperitoneally injected with 0.5 mL of normal sodium twice a week for 8 wk, while the fibrosis model group was injected with equal volume of pig serum for the same duration. At the beginning of the 5^th week, the fibrosis model group was further randomly divided into a fibrosis model subgroup, a rIL-10 gene therapy subgroup and an empty vector control subgroup. Rats in the normal control group and fibrosis model subgroup were injected with Ringer's solution (as a reagent control) via the tail vein weekly, the rIL-10 gene therapy subgroup was injected with rIL-10 plasmid pcDNA3-rIL-10, and the empty vector control subgroup was injected with empty vector pcDNA3. All rats were sacrificed at the end of the 8^th week, and liver tissue samples were collected to observe pathological changes in liver tissue by HE staining and to detect the expression of TNF-α, PDGF-β and COX-2 in liver tissue by immunohistochemistry.

RESULTS: Histopathology analysis proved that experimental liver fibrosis was induced successfully with pig serum. Compared with the fibrosis model subgroup and empty vector control subgroup, the rIL-10 gene therapy subgroup showed mild liver cell degeneration, decreased inflammatory cell infiltration and collagen deposition. Compared with the normal control group, the expression of TNF-α, PDGF-β and COX-2 was significantly increased in the fibrosis model subgroup and empty vector control subgroup (0.2206 ± 0.0434, 0.2217 ± 0.0518 vs 0.1860 ± 0.0104; 0.2891 ± 0.0417, 0.2818 ± 0.0272 vs 0.2514 ± 0.0228; 0.2174 ± 0.0429, 0.2117 ± 0.0221 vs 0.1987 ± 0.0106, all P < 0.01). Compared with the fibrosis model subgroup and empty vector control subgroup, the expression of TNF-α, PDGF-β and COX-2 was significantly reduced in the rIL-10 gene therapy subgroup (0.2048 ± 0.0124 vs 0.2206 ± 0.0434, 0.2217 ± 0.0518; 0.2513 ± 0.0165 vs 0.2891 ± 0.0417, 0.2818 ± 0.0272; 0.1961 ± 0.0142 vs 0.2174 ± 0.0429, 0.2117 ± 0.0221, all P < 0.01).

CONCLUSION: rIL-10 gene treatment attenuates pig serum-induced liver fibrosis in rats possibly by reducing the expression of TNF-α, PDGF-β and COX-2 in liver tissue.

Salvianolic acid B inhibits hepatic stellate cell activation through transforming growth factor beta-1 signal transduction pathway in vivo and in vitro

Salvianolic acid B (Sal B) is a major water soluble component extracted from Radix Salviae miltiorrhizae, a traditional Chinese herb widely used for treating cardiovascular and hepatic diseases. Sal B has been reported to inhibit transforming growth factor (TGF)-β1-stimulated hepatic stellate cells (HSCs) activation and collagen type I expression. In this study, we further investigated the mechanisms of Sal B on liver fibrosis relating to TGF-β/Smads signalling pathway, especially to TGF-β1 receptors. Liver fibrosis model was induced by intraperitoneal injection of dimethylnitrosamine (DMN) for four weeks. Rats were randomly divided into three groups: normal, model, and Sal B groups. Rats in Sal B group were treated by oral administration of Sal B for four weeks from the first day of DMN exposure. Hydroxyproline (Hyp) content in liver tissue was assayed using Jamall's method and collagen deposition was visualized using Sirius red staining. HSCs were isolated from normal rats, and were cultured primarily in uncoated plastics. At day 4 after isolation, cells were stimulated with 2.5 ng/mL TGF-β1, and treated with 1 and 10 µmol/L Sal B and 10 µmol/L SB-431542 (TβR-I inhibitor) for 24 h, respectively. Cell proliferation was examined with 5-ethynyl-2'-deoxyuridine assay. The expressions of alpha smooth muscle actin (α-SMA) and Smad3 were assayed by immunofluorescent stain and Western blotting. The expression of TβR-I was analysed by Western blotting and real-time polymerase chain reaction. The activity of TβR-I kinase was measured by ADP-Glo kinase assay. The results showed that Sal B could inhibit collagen deposition and reduce Hyp content significantly, and decrease expressions of TGF-β1 and TβR-I in fibrotic liver in vivo. Also, Sal B decreased the expressions of α-SMA and TβR-I, inhibited Smad3 nuclear translocation and down-regulated TβR-I kinase activity in vitro. These findings suggested that Sal B could prevent HSCs activation through TGF-β signalling pathway, i.e. inhibiting TGF-β1 expression, activity of TβR-I kinase and Smads phosphorylation.

IL-17A plays a critical role in the pathogenesis of liver fibrosis through hepatic stellate cell activation

Liver fibrosis is a severe, life-threatening clinical condition resulting from nonresolving hepatitis of different origins. IL-17A is critical in inflammation, but its relation to liver fibrosis remains elusive. We find increased IL-17A expression in fibrotic livers from HBV-infected patients undergoing partial hepatectomy because of cirrhosis-related early-stage hepatocellular carcinoma in comparison with control nonfibrotic livers from uninfected patients with hepatic hemangioma. In fibrotic livers, IL-17A immunoreactivity localizes to the inflammatory infiltrate. In experimental carbon tetrachloride-induced liver fibrosis of IL-17RA-deficient mice, we observe reduced neutrophil influx, proinflammatory cytokines, hepatocellular necrosis, inflammation, and fibrosis as compared with control C57BL/6 mice. IL-17A is produced by neutrophils and T lymphocytes expressing the Th17 lineage-specific transcription factor Retinoic acid receptor-related orphan receptor γt. Furthermore, hepatic stellate cells (HSCs) isolated from naive C57BL/6 mice respond to IL-17A with increased IL-6, α-smooth muscle actin, collagen, and TGF-β mRNA expression, suggesting an IL-17A-driven fibrotic process. Pharmacologic ERK1/2 or p38 inhibition significantly attenuated IL-17A-induced HSC activation and collagen expression. In conclusion, IL-17A(+) Retinoic acid receptor-related orphan receptor γt(+) neutrophils and T cells are recruited into the injured liver driving a chronic, fibrotic hepatitis. IL-17A-dependent HSC activation may be critical for liver fibrosis. Thus, blockade of IL-17A could potentially benefit patients with chronic hepatitis and liver fibrosis.

Anchoring hepatic gene expression with development of fibrosis and neoplasia in a toxicant-induced fish model of liver injury

Fish have been used as laboratory models to study hepatic development and carcinogenesis but not for pathogenesis of hepatic fibrosis. In this study, a dimethylnitrosamine-induced fish model of hepatic injury was developed in Japanese medaka (Oryzias latipes) and gene expression was anchored with the development of hepatic fibrosis and neoplasia. Exposed livers exhibited mild hepatocellular degenerative changes 2 weeks' postexposure. Within 6 weeks, hepatic fibrosis/cirrhosis was evident with development of neoplasia by 10 weeks. Stellate cell activation and development of fibrosis was associated with upregulation of transforming growth factor beta 1 (tgfb1), tgfb receptor 2, mothers against decapentaplegic homolog 3 (smad3a), smad3b, beta-catenin (ctnnb1), myc, matrix metalloproteinase (mmp2), mmp14a, mmp14b, tissue inhibitors of metalloproteinase (timp) 2a, timp2b, timp3, collagen type I alpha 1a (col1a1a), and col1a1b and a less pronounced increase in mmp13 and col4a1 expression. Tgfb receptor I expression was unchanged. Immunohistochemistry suggested that biliary epithelial cells and stellate cells were the main producers of TGF-β1. This study identified a group of candidate genes likely to be involved in the development of hepatic fibrosis and demonstrated that the TGF-β pathway likely plays a major role in the pathogenesis. These results support the medaka as a viable fish model of hepatic fibrosis.

Plasmin triggers a switch-like decrease in thrombospondin-dependent activation of TGF-β1

Transforming growth factor-β1 (TGF-β1) is a potent regulator of extracellular matrix production, wound healing, differentiation, and immune response, and is implicated in the progression of fibrotic diseases and cancer. Extracellular activation of TGF-β1 from its latent form provides spatiotemporal control over TGF-β1 signaling, but the current understanding of TGF-β1 activation does not emphasize cross talk between activators. Plasmin (PLS) and thrombospondin-1 (TSP1) have been studied individually as activators of TGF-β1, and in this work we used a systems-level approach with mathematical modeling and in vitro experiments to study the interplay between PLS and TSP1 in TGF-β1 activation. Simulations and steady-state analysis predicted a switch-like bistable transition between two levels of active TGF-β1, with an inverse correlation between PLS and TSP1. In particular, the model predicted that increasing PLS breaks a TSP1-TGF-β1 positive feedback loop and causes an unexpected net decrease in TGF-β1 activation. To test these predictions in vitro, we treated rat hepatocytes and hepatic stellate cells with PLS, which caused proteolytic cleavage of TSP1 and decreased activation of TGF-β1. The TGF-β1 activation levels showed a cooperative dose response, and a test of hysteresis in the cocultured cells validated that TGF-β1 activation is bistable. We conclude that switch-like behavior arises from natural competition between two distinct modes of TGF-β1 activation: a TSP1-mediated mode of high activation and a PLS-mediated mode of low activation. This switch suggests an explanation for the unexpected effects of the plasminogen activation system on TGF-β1 in fibrotic diseases in vivo, as well as novel prognostic and therapeutic approaches for diseases with TGF-β dysregulation.

Novel non-canonical TGF-β signaling networks: emerging roles in airway smooth muscle phenotype and function

The airway smooth muscle (ASM) plays an important role in the pathophysiology of asthma and chronic obstructive pulmonary disease (COPD). ASM cells express a wide range of receptors involved in contraction, growth, matrix protein production and the secretion of cytokines and chemokines. Transforming growth factor beta (TGF-β) is one of the major players in determining the structural and functional abnormalities of the ASM in asthma and COPD. It is increasingly evident that TGF-β functions as a master switch, controlling a network of intracellular and autocrine signaling loops that effect ASM phenotype and function. In this review, the various elements that participate in non-canonical TGF-β signaling, including MAPK, PI3K, WNT/β-catenin, and Ca(2+), are discussed, focusing on their effect on ASM phenotype and function. In addition, new aspects of ASM biology and their possible association with non-canonical TGF-β signaling will be discussed.

Lipopolysaccharide enhances transforming growth factor β1-induced platelet-derived growth factor-B expression in bile duct epithelial cells

BACKGROUND AND AIM

Platelet-derived growth factor (PDGF)-B is a potent profibrogenic mediator expressed by bile duct epithelial cells (BDECs) that contributes to liver fibrosis after bile duct ligation. However, the mechanism of PDGF-B induction in BDECs during cholestasis is not known. Transforming growth factor β (TGFβ) and lipopolysaccharide (LPS) also contribute to the profibrogenic response after bile duct ligation. We tested the hypothesis that LPS and TGFβ1 synergistically induce PDGF-B expression in BDECs.

METHODS

Transformed human BDECs (MMNK-1 cells) and primary rat BDECs were stimulated with LPS and/or TGFβ1, and signaling pathways through which LPS potentiates TGFβ1-induced PDGF-B mRNA expression were investigated.

RESULTS

Stimulation of MMNK-1 cells with LPS alone did not significantly induce PDGF-B mRNA expression. However, LPS co-treatment enhanced TGFβ1 induction of PDGF-B mRNA in MMNK-1 cells and also in primary rat BDECs. Importantly, co-treatment of MMNK-1 cells with LPS and TGFβ1 also significantly increased PDGF-BB protein expression. Interestingly, LPS did not affect TGFβ1 activation of a SMAD-dependent reporter construct. Rather, stimulation of MMNK-1 cells with LPS, but not TGFβ1, increased JNK1/2 phosphorylation. Expression of dominant negative JNK2, but not dominant negative JNK1, inhibited the LPS potentiation of TGFβ1-induced PDGF-B mRNA expression in MMNK-1 cells. In addition, LPS treatment caused IκBα degradation and activation of a nuclear factor κB (NFκB)-dependent reporter construct. Expression of an IκBα super repressor inhibited activation of NFκB and attenuated LPS potentiation of TGFβ1-induced PDGF-B mRNA.

CONCLUSIONS

The results indicate that LPS activation of NFκB and JNK2 enhances TGFβ1-induced PDGF-B expression in BDECs.

Subsynovial connective tissue is sensitive to surgical interventions in a rabbit model of carpal tunnel syndrome

The most common histological finding in carpal tunnel syndrome (CTS) is non-inflammatory fibrosis and thickening of the subsynovial connective tissue (SSCT) in the tunnel. While the cause of SSCT fibrosis and the relationship of SSCT fibrosis and CTS are unknown, one hypothesis is that SSCT injury causes fibrosis, and that the fibrosis then leads to CTS. We investigated the sensitivity of the SSCT to injuries. Two types of surgical interventions were performed in a rabbit model: A skin incision with tendon laceration and SSCT stretching sufficient to damage the SSCT, and skin incision alone. Twelve weeks after surgery, the rabbit carpal tunnel tissues were studied with immunochemistry for TGF-β receptors 1, 2, and 3, collagen III, and collagen VI. All TGF-β receptors were expressed. The percentages of the TGF-β receptors' expressions were less in the control SSCT fibroblasts than in the fibroblasts from rabbits with surgical interventions. The surgical interventions did not result in any alteration of collagen III expression. However, both surgical interventions resulted in a significant decrease in collagen VI expression compared to the control group. The two surgical interventions achieved similar expression of TGF-β receptors and collagens. Our results provide evidence that the SSCT is sensitive to surgical interventions, even when these are modest. Since SSCT fibrosis is a hallmark of CTS, these data also suggest that such fibrosis could result from relatively minor trauma.

Enhanced effect of soluble transforming growth factor-beta receptor II and IFN-gamma fusion protein in reversing hepatic fibrosis

Objective

To examine the in vivo anti-fibrotic effect of rat soluble transforming growth factor β receptor II (RsTβRII) and IFN-γ fusion protein (RsTβRII-IFN-γ) in rat hepatic fibrosis model.

Methods

Model rats were divided into five groups and treated i.m. for 8 weeks: 1) fibrotic model group (each rat, 100 μl of 0.9% NaCl day^-1); 2) RsTβRII-IFN-γ treatment group (each rat, 0.136 mg· day^-1); 3) IFN-γ treatment group (each rat, 7.5 MU· day^-1); 4) RsTβRII treatment group (each rat, 0.048 mg· day^-1); and 5) mixture of IFN-γ and RsTβRII treatment group (each rat, IFN-γ 7.5 MU· day^-1+ RsTβRII 0.048 mg· day^-1). After treatment, hepatic fibrogenesis was evaluated by histopathological analysis and measurement of collagen III, α-smooth muscle actin (α-SMA), TGF-β1, TGF-βRII and their mRNA.

Results

Immunohistochemistry, Western blot and real-time RT-PCR showed that RsTβRII-IFN-γ treatment significantly inhibited liver expression of collagen III, α-SMA, TGF-β1 and TGF-βRII at both protein and mRNA levels. Histopathological analysis also showed that the enhanced anti-fibrotic effects were achieved in model rats treated with RsTβRII-IFN-γ.

Conclusion

Our results confirmed that RsTβRII-IFN-γ has the enhanced effects in reversing hepatic fibrosis.

Neuropilin-1 mediates divergent R-Smad signaling and the myofibroblast phenotype

The transforming growth factor-beta (TGF-β) superfamily is one of the most diversified cell signaling pathways and regulates many physiological and pathological processes. Recently, neuropilin-1 (NRP-1) was reported to bind and activate the latent form of TGF-β1 (LAP-TGF-β1). We investigated the role of NRP-1 on Smad signaling in stromal fibroblasts upon TGF-β stimulation. Elimination of NRP-1 in stromal fibroblast cell lines increases Smad1/5 phosphorylation and downstream responses as evidenced by up-regulation of inhibitor of differentiation (Id-1). Conversely, NRP-1 loss decreases Smad2/3 phosphorylation and its responses as shown by down-regulation of α-smooth muscle actin (α-SMA) and also cells exhibit more quiescent phenotypes and growth arrest. Moreover, we also observed that NRP-1 expression is increased during the culture activation of hepatic stellate cells (HSCs), a liver resident fibroblast. Taken together, our data suggest that NRP-1 functions as a key determinant of the diverse responses downstream of TGF-β1 that are mediated by distinct Smad proteins and promotes myofibroblast phenotype.

Inhibition of hepatic stellate cells proliferation by mesenchymal stem cells and the possible mechanisms

AIM

During fibrosis, hepatic stellate cells (HSCs) undergo a complex activation process characterized by increased proliferation and extracellular matrix deposition. Previous studies have suggested that mesenchymal stem cells (MSCs) may ameliorate fibrogenesis and represent a promising strategy for cell therapy. However, the underlying mechanisms are not fully understood.

METHODS

Hepatic stellate cells were treated with or without MSCs. Then cell proliferation and cell cycle were analyzed. Production of soluble factors by MSCs and its relation with cell proliferation suppression was evaluated by transwell co-culture and RNA interference. Effects of MSCs on the gene expression of collagen were also evaluated.

RESULTS

MSCs induced G(0)/G(1) arrest of HSCs growth partly through secreting soluble factors TGF-beta3 and HGF, which resulted in up-regulation of p21(Cip1) and p27(Kip1) expression and down-regulation of cyclinD1. MSCs inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and reduced gene expression of collagen type I and III. MSCs did not reverse the proliferation and collagen type I gene expression of HSCs provoked by PDGF.

CONCLUSIONS

The growth inhibition of HSCs induced by MSCs through an arrest in the G(0)/G(1) phase of the cell cycle is partially mediated by secretion of TGF-beta3 and HGF. MSCs inhibit HSCs activation through decreasing phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. These results further support MSCs may be used as a novel therapy for treating fibrotic diseases in human.

Established neointimal hyperplasia in vein grafts expands via TGF-beta-mediated progressive fibrosis

In weeks to months following implantation, neointimal hyperplasia (NIH) in vein grafts (VGs) transitions from a cellularized to a decellularized phenotype. The inhibition of early cellular proliferation failed to improve long-term VG patency. We have previously demonstrated that transforming growth factor-beta(1) (TGF-beta(1))/connective tissue growth factor (CTGF) pathways mediate a conversion of fibroblasts to myofibroblasts in the early VG (<2 wk). We hypothesize that these similar pathways drive fibrosis observed in the late VG lesion. Within rabbit VGs, real-time RT-PCR, Western blot analysis, ELISA, and immunohistochemistry were used to examine TGF-beta/CTGF pathways in late (1-6 mo) NIH. All VGs exhibited a steady NIH growth (P = 0.006) with significant reduction in cellularity (P = 0.01) over time. Substantial TGF-beta profibrotic activities, as evidenced by enhanced TGF-beta(1) activation, TGF-beta receptor types I (activin receptor-like kinase 5)-to-II receptor ratio, SMAD2/3 phosphorylation, and CTGF production, persisted throughout the observation period. An increased matrix synthesis was accompanied by a temporal reduction of matrix metalloproteinase-2 (P = 0.001) and -9 (P < 0.001) activity. VG NIH is characterized by a conversion from a proproliferative to a profibrotic morphology. An enhanced signaling via TGF-beta/CTGF coupled with reduced matrix metalloproteinase activities promotes progressive fibrotic NIH expansion. The modulation of late TGF-beta/CTGF signaling may offer a novel therapeutic strategy to improve the long-term VG durability.

Antifibrogenic effects of tamoxifen in a rat model of periportal hepatic fibrosis

BACKGROUNDS/AIMS

It has been reported that tamoxifen may affect hepatoma cell growth in vitro by suppressing transforming growth factor beta-1 (TGF-beta1) expression, suggesting that tamoxifen might also retard fibrogenesis. Thus, we examined whether tamoxifen might suppress TGF-beta1 expression and consequently inhibit the process of hepatic fibrosis in vivo.

METHODS

To induce periportal hepatic fibrosis, 50 male adult Sprague-Dawley rats were injected with 0.62 mmol/kg of allyl alcohol, intraperitoneally, twice a week for 8 weeks. Hepatic fibrosis scores, intrahepatic collagen levels and plasma TGF-beta1 expression levels were evaluated in three groups of 10 rats orally administered tamoxifen at 1, 5 and 10 mg/kg, respectively, and in 20 controls. Messenger RNAs (mRNAs) encoding TGF-beta1 and TGF-beta receptors in liver tissue were semiquantified using reverse transcriptase polymerase chain reaction.

RESULTS

Hepatic fibrosis scores decreased progressively as the dose of tamoxifen increased, resulting in a significant change in rats treated with tamoxifen at 10 mg/kg compared with controls (P=0.018). Intrahepatic collagen content was significantly less in the group treated with tamoxifen at 10 mg/kg compared with the control (P=0.045). Plasma TGF-beta1 levels were also significantly lower in rats treated with tamoxifen at 10 mg/kg compared with controls (P=0.007). All three concentrations of tamoxifen tested decreased the expression levels of hepatic TGF-beta1 mRNA and type I TGF-beta receptor (TGF-beta RI) mRNA to similar extents.

CONCLUSIONS

Tamoxifen seems to inhibit the process of hepatic fibrosis dose-dependently by suppressing the transcription of TGF-beta1 and TGF-beta RI in an experimental model of periportal hepatic fibrosis.

Down-regulation of TGFbeta1 and leptin ameliorates thioacetamide-induced liver injury in lipopolysaccharide-primed rats

Pretreatment with a low dose of bacterial endotoxin (lipopolysaccharide, LPS) caused the reduction of cytochrome P450 (CYP) enzymes and inflammatory factors which are capable of protecting the liver from a lethal LPS challenge. However, the effects of LPS pretreatment on the expression of transforming growth factor beta1 (TGFbeta1) and leptin in thioacetamide (TAA)-induced liver fibrosis remain unknown. In this study, Sprague-Dawley rats were pretreated intraperitoneally with LPS (5 mg/kg body weight) for 24 h, and subsequently treated with TAA (200 mg/kg body weight/ 3 days) for 1 month to examine the effects of LPS on TAA-injured rats. LPS pretreatment was associated with lower granulation and lower (P < 0.05) GOT/GPT than in TAA-injured rats. The LPS-pretreated group had less collagen (Sirius red histochemical staining). Semiquantitative RT-PCR showed that the levels of collagen 3 and TGFbeta1 mRNAs were lower (P < 0.05) in the liver of LPS-pretreated rats than in TAA-injured rats. TGFbetaRI mRNA in the liver of LPS-pretreated rats exceeded (P < 0.05) that in TAA-injured rats. LPS pretreatment reduced the leptin content (Western blot) below that of TAA-injured rats. These results imply that LPS pretreatment (endotoxin tolerance) alleviates the TAA-induced liver fibrosis of rats by reducing TGFbeta1 and leptin content.

Autocrine TGF-beta signaling in the pathogenesis of systemic sclerosis

Excessive extracellular matrix deposition in the skin, lung, and other organs is a hallmark of systemic sclerosis (SSc). Fibroblasts isolated from sclerotic lesions in patients with SSc and cultured in vitro are characterized by increased synthesis of collagen and other extracellular matrix components, consistent with the disease phenotype. Thus, cultured scleroderma fibroblasts serve as a principal experimental model for studying the mechanisms involved in extracellular matrix overproduction in SSc. The pathogenesis of SSc is still poorly understood, but increasing evidence suggests that transforming growth factor-beta (TGF-beta) is a key mediator of tissue fibrosis as a consequence of extracellular matrix accumulation in the pathology of SSc. TGF-beta regulates diverse biological activities including cell growth, cell death or apoptosis, cell differentiation, and extracellular matrix synthesis. TGF-beta is known to induce the expression of extracellular matrix proteins in mesenchymal cells and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the extracellular matrix. This review focuses on the possible role of autocrine TGF-beta signaling in the pathogenesis of SSc.

Hepatic stellate cell activation in liver transplant patients with hepatitis C recurrence and in non-transplanted patients with chronic hepatitis C

The pathogenic mechanisms of accelerated graft fibrosis in hepatitis C recurrence after liver transplantation (LT) are not well established. The aim of the study was to assess whether a greater activation of hepatic stellate cells (HSC), the major collagen-producing cells in the liver, can occur in these patients as compared to non-LT patients with chronic hepatitis C. We determined the amount of activated HSC by computer-based morphometric analysis of alpha-smooth muscle actin (alphaSMA)-positive cells and the hepatic TGFbeta(1) expression by immunohistochemistry in 46 LT patients with hepatitis C recurrence, 35 non-LT patients with chronic hepatitis C, and 16 controls. Hepatic alphaSMA and TGFbeta(1) expression was higher in LT patients with hepatitis C recurrence than in controls and was correlated with fibrosis stage and progression rate. No significant difference in alphaSMA and TGFbeta(1) expression was observed between LT and non-LT patients with hepatitis C, with the exception of a higher transforming growth factor beta-1 (TGFbeta(1)) expression in non-LT patients in the early stages of fibrosis. LT patients receiving cyclosporine (CsA) or tacrolimus (FK) had a similar fibrosis progression rate and alphaSMA and TGFbeta(1) expression. In conclusion, the accelerated fibrosis observed in LT patients with hepatitis C recurrence does not seem to be related to a greater amount of activated HSC and TGFbeta(1) expression in the grafts of these patients as compared to non-LT patients with chronic hepatitis C. In LT patients, the amount of activated HSC and TGFbeta(1) expression correlated with fibrosis stage and progression, without any apparent influence of the type of calcineurin inhibitor administered.

Prostacyclin in liver disease: a potential therapeutic option

Complex molecular and cellular mechanisms are involved in the initiation and progression of hepatic fibrosis. Recent studies have shown that hepatic stellate cells, endothelin, cytokines and prostacyclin play crucial roles in this pathology. Prostacyclin exerts vasorelaxant, antioxidant and antifibrotic properties that prevent the development of fibrosis and cirrhosis in liver diseases. In this editorial, the authors discuss some of the molecular and cellular mechanisms involved in the initiation and progression of liver fibrosis and the role played by prostacyclin in counteracting it. At the moment, however, only limited information is available from clinical studies demonstrating the effectiveness of prostacyclin in liver diseases and this makes it difficult to draw any conclusions; further efforts are necessary to verify whether prostacyclin, alone or in combination with other drugs, may be a valid therapeutic option in liver diseases.

JinSanE decoction, a chinese herbal medicine, inhibits expression of TGF-beta1/Smads in experimental hepatic fibrosis in rats

The study is to investigate the effects of a Chinese herbal medicine, JinSanE decoction, on the TGF-beta1/Smads signal transduction pathway in a carbon tetrachloride (CCl(4))-induced hepatic fibrosis model in rats. Rats were randomly divided into 4 study groups: namely, a normal control group, a hepatic fibrosis model group, and 2 treatment groups with different doses of JinSanE (6 and 12 g/kg). Ten rats in each group were sacrificed at 4 and 8 weeks after exposure to CCl(4) respectively. The levels of TGF-beta1 and TRII mRNA in liver tissue were analyzed by RT-PCR. The expressions of TGF-beta1, Smad3 and Smad7 in liver tissues were evaluated by immunohistochemistry. The liver histopathology was examined by hematoxylin and eosin (HE) staining and electron microscopy respectively. The liver hydroxyproline (HYP), liver function and hyaluronic acid (HA) were examined by biochemistry and radioimmunoassay (RIA) respectively. Compared with the hepatic fibrosis model group, the levels of TGF-beta1, TRII mRNA and Smad3 expression significantly decreased in the 2 treatment groups. The expression of Smad7 was significantly increased in the liver of the rats treated with JinSanE (p < 0.05 or p < 0.01). The histological changes of fibrotic liver were obviously improved in the treatment rats. The levels of liver HYP, serum liver function and HA were also remarkably improved in the treatment rats. Moreover, the effects of JinSanE occurred in a dose- and time-dependent manner in the process of the protection of liver injury and fibrosis. JinSanE decoction had a protective effect on liver injury and could ameliorate hepatic fibrosis in rats. The mechanisms might be associated with their effects of down-regulating TGF-beta1, TRII mRNA and Smad3, and up-regulating Smad7.

Transforming growth factor-beta receptor type I-dependent fibrogenic gene program is mediated via activation of Smad1 and ERK1/2 pathways

The transforming growth factor (TGF)-beta/Smad3 signaling pathway is considered a central mediator of pathological organ fibrosis; however, contribution of Smad2/3-independent TGF-beta signaling has not been fully explored. The present study utilized previously a described model of scleroderma (SSc) fibrosis based on forced expression of the TGF-betaRI (ALK5) (Pannu, J., Gardner, H., Shearstone, J. R., Smith, E., and Trojanowska, M. (2006) Arthritis Rheum. 54, 3011-3021). This study was aimed at determining the molecular mechanisms underlying the profibrotic program in this model. We demonstrate that the TGF-betaRI-dependent up-regulation of collagen and CCN2 (CTGF) does not involve Smad2/3 activation but is mediated by ALK1/Smad1 and ERK1/2 pathways. The following findings support this conclusion: (i) Smad2 and -3 were not phosphorylated in response to TGF-betaRI, (ii) a TGF-betaRI mutant defective in Smad2/3 activation, ALK5(3A), potently stimulated collagen production, (iii) elevation of TGF-betaRI triggered sustained association of ALK5 with ALK1 and high levels of Smad1 phosphorylation, (iv) blockade of Smad1 via small interfering RNA abrogated collagen and CCN2 up-regulation in this model, (v) elevated TGF-betaRI led to a prolonged activation of ERK1/2, (vi) the pharmacologic inhibitor of ERK1/2 inhibited Smad1 phosphorylation and abrogated profibrotic effects of elevated TGFbeta-RI. Additional experiments demonstrated that a GC-rich response element located -6 to -16 (upstream of the transcription start site) in the CCN2 promoter mediated Smad1-dependent increased promoter activity in this model. This element was shown previously to mediate up-regulation of the CCN2 promoter in SSc fibroblasts. In conclusion, this study defines a novel ALK1/Smad1- and ERK1/2-dependent, Smad3-independent mode of TGF-beta signaling that may operate during chronic stages of fibrosis in SSc.

Epidermal growth factor up-regulates transforming growth factor-beta receptor type II in human dermal fibroblasts via p38 mitogen-activated protein kinase pathway

TGF-beta receptors (TbetaRs) are serine/threonine kinase receptors that bind to TGF-beta and propagate intracellular signaling through Smad proteins. TbetaRs are repressed in some human cancers and expressed at high levels in several fibrotic diseases. We demonstrated that epidermal growth factor (EGF) up-regulates type II TGF-beta receptor (TbetaRII) expression in human dermal fibroblasts. EGF-mediated induction of TbetaRII expression was inhibited by the treatment of fibroblasts with a specific p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, whereas MEK inhibitor PD98059 did not block the up-regulation of TbetaRII by EGF. EGF induced the TbetaRII promoter activity, and this induction was significantly blocked by SB203580, but not by PD98059. The overexpression of the dominant negative form of p38alpha or p38beta significantly reduced the induction of TbetaRII promoter activity by EGF. These results indicate that the EGF-mediated induction of TbetaRII expression involves the p38 MAPK signaling pathway. The EGF-mediated induction of TbetaRII expression may participate in a synergistic interplay between EGF and TGF-beta signaling pathway.

Abnormal expression of Smurf2 during the process of rat liver fibrosis

OBJECTIVE

Liver fibrosis is a prelude of liver cirrhosis. Currently the molecular mechanism of liver fibrosis is not clear. The purpose of this study is to screen the abnormally expressed genes of liver fibrosis and to illustrate the changes of Smurf2 expression in the process of liver fibrosis.

METHODS

A liver fibrosis model was established in rats by injection of tetrachlormethane (CCl(4)). A cDNA microarray analysis was performed on the liver at mid-stage of fibrosis. Thereafter, a semi-quantitative RT-PCR, Western blot analysis and immunohistochemistry test were performed for determining Smurf2, Smad2 and SnoN at week 1, 2, 4 and 8 of establishing the liver fibrosis model.

RESULTS

Smurf2, FGG, PTAFR, CYP2D6, among others, increased in the fibrosis liver and a semi-quantitative RT-PCR confirmed the reliability of the cDNA microarray analysis. Smurf2 in the liver fibrosis model group was at the same level as that of control group at week 1, but decreased at week 2 and 8 and increased at the week 4. Smad2 increased at week 2 and 8 but increased at week 4. However, Smad2 mRNA increased to the same level at week 4 as that at week 2 and 8. The decrease of Smad2 at week 4 may be due to the enhancement of ubiquitination and proteolytic degradation of Smad2 by the increase of Smurf2. SnoN decreased at week 4 and 8 because of the ubiquitination and degradation caused by Smurf2. The decrease of SnoN may explain the progress of liver fibrosis in spite of the decrease of Smad2 at week 4.

CONCLUSION

This study screened the abnormally expressed genes of liver fibrosis and illustrated the changes of Smurf2, Smad2 and SnoN during the process of liver fibrosis.

Effects of perindopril and valsartan on expression of transforming growth factor-beta-Smads in experimental hepatic fibrosis in rats

BACKGROUND

Previous studies have shown that the renin-angiotensin system (RAS) plays an important role in the pathogenesis of hepatic fibrosis, and blockers of the RAS may be active as an antifibrogenic goal. However, the potential role of RAS inhibition on expression transforming growth factor (TGF)-beta-Smads in hepatic fibrosis remains unknown. The aim of this study was to investigate the effect and mechanism of an angiotensin-converting enzyme inhibitor (perindopril) and an angiotensin II receptor blocker (valsartan) on TGF-beta1 and TGF receptor II (TRII) mRNA, Smad3 and Smad7 in fibrotic hepatic livers in rats.

METHODS

Sixty Wistar rats were randomly divided into four study groups (n = 15 for each group), including normal controls, hepatic fibrosis models, and two treated groups with either perindopril or valsartan, starting from the fourth week after being exposed to carbon tetrachloride (CCl(4)) for 4 weeks. The levels of TGF-beta and TRII mRNA in liver tissue were analyzed by RT-PCR. The expressions of TGF-beta1, Smad3 and Smad7 in liver tissues were evaluated by immunohistochemistry. The liver histopathology was examined by hematoxylin and eosin (HE) staining and by electron microscopy, respectively. The liver function and serum hyaluronic acid were also assayed by biochemistry and radioimmunoassay.

RESULTS

Compared with the hepatic fibrosis models, the levels of TGF-beta1, TRII mRNA and the expression Smad3 significantly decreased in the two treated groups, and the expression of Smad7 was significantly increased in the liver of rats treated with perindopril or valsartan (P < 0.05 or P < 0.01). The histological changes and ultrastructure of fibrotic liver, liver function and hyaluronic acid also remarkably improved in the treated rats.

CONCLUSIONS

The angiotensin-converting enzyme inhibitors perindopril and valsartan have a protective effect on liver injury and can ameliorate hepatic fibrosis in rats induced by CCl(4). The mechanisms may be associated with their effects of down-regulating TGF-beta1, TRII mRNA and smad3, and up-regulating Smad7.

Direct activation of TGF-beta1 transcription by androgen and androgen receptor complex in Huh7 human hepatoma cells and its tumor in nude mice

Importance of androgen for promotion of hepatocelullar carcinoma (HCC) has long been supported by clinical and experimental evidences. However, mechanisms involved in the carcinogenesis have not yet been fully elucidated. Moreover, unbalanced expression of TGF-beta1 during tumor progression results in prooncogenic rather than growth inhibition. To investigate the effect of androgen on transcriptional regulation of TGF-beta1, we isolated rat TGF-beta1 promoter, based on our previous report (GenBank AF249327), and examined regulation of its promoter activity by dihydrotestosterone in Huh7, LNCaP, and PC3 cells. Several putative transcription factor-binding sites were found, but no TATA box. When the full-length (-4784 to +68) and variously deleted promoter DNAs were evaluated, the promoter region spanning from -2732 to -1203 showed the highest activity towards dihydrotestosterone in a dose-dependent manner in both Huh7 and PC3 cells with androgen receptor (AR) expression. Putative androgen response sequence half site (5'-TGTCCT-3') was identified to be located within -1932 to -1927, proved by mutant (5'-AGACCT-3') analysis and chromatin immunoprecipitation (ChIP) assay. AR mediated upregulation of TGF-beta1 expression was confirmed by HCC developed in nude mice with AR-overexpressed Huh7-cells. This work presents in vivo and in vitro evidences of activation of TGF-beta1 expression by androgen and AR, and implicates the modulation of hepatocarcinogenesis by AR through the regulation of TGF-beta1 expression.

Anti-TGF-beta strategies for the treatment of chronic liver disease

Permanent alcohol abuse may lead to chronic liver injury with deleterious sequelae such as liver cirrhosis and hepatocellular carcinoma. Mechanisms of fibrogenesis encompass recruitment of inflammatory cells at the site of injury and cytokine mediated activation of hepatic stellate cells (HSC) with accumulation of interstitial collagens. HSC transdifferentiation and accompanying apoptosis result in destruction of liver architecture and are therefore key steps of disease progression. TGF-beta represents the main profibrogenic cytokine in liver fibrosis and other fibroproliferative disorders by inducing extracellular matrix deposition as part of the wound healing response. In parallel, TGF-beta triggers hepatocytes that are strongly responsive for this cytokine, to undergo apoptosis, thereby providing space for HSC proliferation and generation of a collagenous matrix. Anti TGF-beta approaches were established and successfully utilized for the treatment of experimental fibrogenesis. Dominant negative TGF-beta receptors (TbetaR), generated by fusing the Fc domain of human IgG and the N-terminal (extracellular) fragment of TbetaRII (Fc:TbetaRII) were applied to suppress fibrosis. Similarly TGF-beta binding proteins like decorin, antagonistic cytokines such as bone morphogenetic protein-7, hepatocyte growth factor, IL-10, or IFN-gamma were as efficient as camostat mesilate, a protease inhibitor that possibly abrogated proteolytic activation of TGF-beta. Further, our group recently overexpressed Smad7 in bile duct ligation induced liver fibrosis and achieved efficient inhibition of intracellular TGF-beta signaling, thereby counteracting profibrogenic effects in cultured HSC and in vivo. A direct link between the effect of alcohol and TGF-beta exists through reactive oxygen species that are generated in liver cells by alcohol metabolism and represent activators of TGF-beta signaling. Thus, soluble TbetaRII expression reduced experimental fibrogenesis in vitro and in vivo partially by decreasing intracellular ROS and inhibiting NADH oxidase. Approaches that specifically target profibrogenic TGF-beta signaling are promising to treat alcoholic liver disease in the future. However, to ensure safety for the patients to be treated, approaches with strong specificity need to be established. Therefore, it is essential to delineate the profibrogenic actions of TGF-beta and the influence of alcohol abuse in molecular detail.

Plasma transforming growth factor β1, metalloproteinase-1 and tissue inhibitor of metalloproteinases-1 in acute viral hepatitis type B

AIM

Antiproliferative, pro-apoptotic and immunosuppressive activity effects suggest crucial role of transforming growth factor (TGF)-beta1, metalloproteinase (MMP)-1 and its tissue inhibitor (TIMP)-1 in the pathogenesis of acute liver injury that in some patients precede development of chronic liver diseases and fibrogenesis. The aim of this study was to evaluate effect of acute HBV infection on plasma TGF-beta1, MMP-1 and TIMP-1 levels.

METHODS

TGF-beta1, MMP-1 and TIMP-1 plasma concentrations were measured with an enzyme immunoassay in 39 patients with acute viral hepatitis type B. Baseline measurement was performed within the first week of jaundice and then weekly up to the fourth week of the disease. Results were compared to baseline and normal values and to liver function tests.

RESULTS

Plasma concentrations of TGF-beta1, TIMP-1 and MMP-1 were significantly elevated in the first week of acute viral B hepatitis in comparison to normal. Analysis of individual values demonstrated significant positive correlation between plasma concentrations of TGF-beta1 and TIMP-1. There was no correlation between MMP-1 and TGF-beta1 or TIMP-1. Significant correlation was demonstrated between both TGF-beta1 and ALT or AST as well as between TIMP-1 and ALT, AST or bilirubin. Elevated baseline levels of both TGF-beta1 and TIMP-1 decreased gradually in consecutive weeks of the disease. TGF-beta1 but not TIMP-1 plasma concentrations were significantly lower in 3rd and 4th week than baseline values. MMP-1 concentration remained on baseline level in the 2nd week of the disease. However in the 3rd week its values increased suddenly but the significant difference in comparison to baseline was observed only in 4th week.

CONCLUSIONS

These results indicate important role of TGF-beta1, TIMP-1 and MMP-1 in acute viral hepatitis, that seems to be connected first of all with hepatocytes damage. Their role in extracellular matrix metabolism during acute liver injury needs further evaluation.

Smad2 and Smad3 play different roles in rat hepatic stellate cell function and alpha-smooth muscle actin organization

Hepatic stellate cells (HSC) play a central role in the pathogenesis of liver fibrosis, transdifferentiating in chronic liver disease from "quiescent" HSC to fibrogenic myofibroblasts. Transforming growth factor-beta (TGF-beta), acting both directly and indirectly, is a critical mediator of this process. To characterize the function of the TGF-beta signaling intermediates Smad2 and Smad3 in HSC, we infected primary rat HSC in culture with adenoviruses expressing wild-type and dominant negative Smads 2 and 3. Smad3-overexpressing cells exhibited increased deposition of fibronectin and type 1 collagen, increased chemotaxis, and decreased proliferation compared with uninfected cells and those infected with Smad2 or either dominant negative, demonstrating different biological functions for the two Smads. Additionally, coinfection experiments suggested that Smad2 and Smad3 signal via independent pathways. Smad3-overexpressing cells as well as TGF-beta-treated cells demonstrated more focal adhesions and increased alpha-smooth muscle actin (alpha-SMA) organization in stress fibers, although all cells reached the same level of alpha-SMA expression, indicating that Smad3 also regulates cytoskeletal organization in HSC. We suggest that TGF-beta, signaling via Smad3, plays an important role in the morphological and functional maturation of hepatic myofibroblasts.

Effects of Chinese traditional compound, JinSanE, on expression of TGF-β1 and TGF-β1 type II receptor mRNA, Smad3 and Smad7 on experimental hepatic fibrosis in vivo

AIM: The transforming growth factor-beta (TGF-β)/Smad signaling pathway system plays a prominent role in the control of cell growth and extracellular matrix formation in the progression of liver fibrogenesis. Smad proteins can either positively or negatively regulate TGF-β responses. In this study, the therapeutic effects of Chinese traditional compound decoction, JinSanE, and the changes of TGF-β/Smad signaling pathway system in carbon tetrachloride (CCl₄)-induced rat experimental liver fibrosis were examined.

METHODS: Seventy-two healthy Wistar rats were assigned to groups including normal control group, CCl₄ model group, JinSanE treatment group I and JinSanE treatment group II. Each group contained 18 rats. All groups, except the normal control group, received CCl₄ subcutaneous injection for 8 wk. Rats in JinSanE groups I and II were orally treated with JinSanE daily at the 1^st and 5^th wk, respectively, after exposure to CCl₄. The expression of TGF-β1 and TGF-β1 type II receptor (TRII) mRNA in the liver was determined by reverse transcription polymerase chain reaction, and the expression of TGF-β1, Smad3 and Smad7 by immunohistochemistry. The liver histopathology was also examined by HE staining and observed under electron microscope. The activities of several serum fibrosis-associated enzymes, alanine aminotransferase (ALT), aspartate aminotransferase (AST), the levels of serum hyaluronic acid (HA) were assayed.

RESULTS: Hepatic fibrosis caused by CCl₄ was significantly inhibited in the JinSanE-treated groups. The degrees of necrosis/degeneration and fibrosis scores were significantly lower in the JinSanE-treated groups than in the model control group. The expression of TGF-β1, TRII and Smad3 was significantly higher in the model group than that in the JinSanE-treated groups, and the active/total TGF-β1 ratio in the JinSanE groups was suppressed. Expression of TRII mRNA and Smad3 proteins showed a distribution pattern similar to that of TGF-β1 with a direct correlation in terms of the degree of hepatic fibrosis. The amount of positive staining Smad7 cells was significantly less in the model group than in the JinSanE-treated groups and the normal group. The contents of ALT, AST and HA were significantly lower in the JinSanE-treated groups than those in the model group.

CONCLUSION: Traditional Chinese medicine, JinSanE, prevents the progression of hepatic damage and fibrosis through the inhibition of TGF-β1, TRII and Smad3 signal proteins, and increases expression of Smad7 signal protein in vivo.

Activation of the MEK5/ERK5 cascade is responsible for biliary dysgenesis in a rat model of Caroli's disease

Polycystic kidney (PCK) rats exhibit a multiorgan cyst pathology similar to human autosomal recessive polycystic kidney disease, and are proposed as an animal model of Caroli's disease with congenital hepatic fibrosis (CHF). This study investigated the expression and function of selected components of the mitogen activated protein kinase (MAPK) pathway in cultured intrahepatic biliary epithelial cells (BECs) of PCK rats. Compared to the proliferative activity of cultured BECs of control rats, those of the PCK rats were hyperresponsive to epidermal growth factor (EGF). The increase in BEC proliferation was accompanied by overexpression of MAPK/extracellular signal-regulated protein kinase (ERK) kinase 5 (MEK5), and subsequent phosphorylation of ERK5 in vitro. The increased proliferative activity was significantly inhibited by the transfection of short interfering RNA against MEK5 mRNA. An EGF receptor tyrosine kinase inhibitor, gefitinib ("Iressa", ZD1839), also significantly inhibited the abnormal growth of cultured BECs of PCK rats. By contrast, treatment with PD98059 and U0126, inhibitors for MEK1/2, was less effective. These results suggest that the activation of the MEK5-ERK5 cascade plays a pivotal role in the biliary dysgenesis of PCK rats, and also provide insights into the pathogenesis of Caroli's disease with CHF. As the MEK5-ERK5 interaction is highly specific, it may represent a potential target of therapy.

Iloprost: an adjunctive approach to chronic viral hepatitis treatment

Chronic viral liver disease may evolve to cirrhosis. The medical treatment to slow down this passage is based on anti-viral and anti-fibrotic properties of interferon. Recently, we evidenced significant increase of portal vein flow velocity and volume after a prostacyclin analog (iloprost) infusion in subjects without and with chronic viral hepatitis. On the basis of these results and considering both the pathophysiology of viral liver disease and the mechanism of action of iloprost in portal microcirculation, we hypothesize that it may be of some efficacy in chronic liver disease ameliorating the portal hemodynamics and producing an anti-oxidant liver effect.

Molecular mechanisms of alcohol-induced hepatic fibrosis

Alcohol abuse is a major cause of liver fibrosis and cirrhosis in developed countries. Before alcoholic liver fibrosis becomes evident, the liver undergoes several stages of alcoholic liver disease including steatosis and steatohepatitis. Although the main mechanisms of fibrogenesis are independent of the etiology of liver injury, alcoholic liver fibrosis is distinctively characterized by a pronounced inflammatory response due to elevated gut-derived endotoxin plasma levels, an augmented generation of oxidative stress with pericentral hepatic hypoxia and the formation of cell-toxic and profibrogenic ethanol metabolites (e.g. acetaldehyde or lipid oxidation products). These factors, based on a complex network of cytokine actions, together result in increased hepatocellular damage and activation of hepatic stellate cells, the key cell type of liver fibrogenesis. Although to date removal of the causative agent, i.e. alcohol, still represents the most effective intervention to prevent the manifestation of alcoholic liver disease, sophisticated molecular approaches are underway, aiming to specifically blunt profibrogenic signaling pathways in liver cells or specifically induce cell death in activated hepatic stellate cells to decrease the scarring of the liver.

Effects of c-myb antisense RNA on TGF-β1 and α1-I collagen expression in cultured hepatic stellate cells

AIM: To investigate the effects of c-myb antisense RNA on cell proliferation and the expression of c-myb, TGF-β1 and α1-I collagen in cultured hepatic stellate cells (HSC) from rats.

METHODS: Recombinant retroviral vector of c-myb antisense gene (pDOR-myb) was constructed, and then transfected into retroviral package cell line PA317 by means of DOTAP. The pseudoviruses produced from the resistant PA317 cells were selected with G418 to infect HSCs isolated from rat livers. The cell proliferation was measured by 3-[4, 5-Dimethylthiazolzyl]-2, 5-diphenyl tetrazo-dium bromide (MTT) method.The expression of c-myb, α1-I collagen and TGF-β1 mRNA, and c-myb protein in HSCs was detected with semi-quantitive reverse transeription-polymerase chain reaction (RT-PCR) and Western-blot respectively.

RESULTS: HSCs from rats were isolated successfully with the viability > 98%. In the pDOR-myb infected HSCs, the c-myb protein expression, cell proliferation,and α1-I collagen and TGF-β1 mRNA expression were repressed significantly compared with their corresponding control groups (P < 0.01).

CONCLUSION: c-myb plays a key role in activation and proliferation of HSC. c-myb antisense RNA can inhibit cell proliferation, α1-I collagen and TGF-β1 mRNA expression, suggesting that inhibition of c-myb gene expression might be a potential way for the treatment of liver fibrosis.

Identification of endoglin in rat hepatic stellate cells: new insights into transforming growth factor beta receptor signaling

Transforming growth factor beta (TGF-beta) signaling is mediated by the cell surface TGF-beta type I (ALK5), type II, and the accessory type III receptors endoglin and betaglycan. Hepatic stellate cells (HSC), the most profibrogenic cell type in the liver, express ALK5, TbetaRII, and betaglycan. To monitor the expression of betaglycan in HSC, we used the commercially available antibody sc-6199 in Western blot analysis. This antibody, raised against a peptide mapping at the carboxyl terminus of the human betaglycan, is claimed to be specific for betaglycan, although it is known that the C-terminal domain is highly conserved in type III receptors. Proteins recognized in HSC by sc-6199 did not match the characteristic migration pattern of betaglycan. Moreover, the determined molecular weight (M(r) 160) and the observed reductant sensitivity after treatment with dithiothreitol resemble those of a closely related type III receptor, endoglin (CD105). Endoglin, a disulfide-linked homodimer, is an accessory component of the TGF-beta receptor complex and mainly expressed on endothelial cells. The presence of endoglin in HSC of rat liver was confirmed by molecular cloning of the endoglin cDNA and immunocytochemistry. The reactivity of sc-6199 with both auxiliary TGF-beta receptors (betaglycan and endoglin) from rats was demonstrated by Western blot and immunocytochemical analysis of cells heterologously expressing these proteins. Furthermore, Northern and Western blotting revealed that both betaglycan and endoglin genes are differentially regulated in HSC and in transdifferentiated myofibroblasts (MFB). By surface labeling and immunoprecipitation experiments, we show that endoglin is found in significant amounts exposed at the plasma membrane of HSC and MFB, which is a pivotal prerequisite for binding of and signaling in response to TGF-beta. In conclusion, we hypothesize that TGF-beta signals in HSC and MFB are tuned by two different interconnected signaling pathways, as it was previously demonstrated for endothelial cells.

The Immunology of Fibrogenesis in Alcoholic Liver Disease

Context.—Alcoholic liver disease in humans frequently leads to cirrhosis. Experimental models of hepatic fibrogenesis are available, but extrapolation of those findings to human ethanol-induced liver injury is difficult. Hepatic ethanol-induced fibrosis in humans has often been studied in relatively small patient populations. During the past decade, several animal models and human studies have attributed fibrogenesis in the liver to the role played by hepatocytes, Kupffer cells, endothelial cells, and especially stellate cells.

Objective.—To determine the contribution of the main liver cell types to ethanol-induced fibrogenesis. For that purpose, we studied the expression of the following immunologic parameters: smooth muscle–specific α actin (SMSA), CD68, CD34, transforming growth factor β1, intercellular adhesion molecule 1, and collagen types 1 and 3. The Dako LSAB+ kit (peroxidase method) was used.

Design.—We recently studied a large cohort of patients with alcoholic liver disease in France. In this cohort, we found 87 cases in which liver biopsies revealed only pericentral injury with nonpathologic portal areas. We compared cases in which the portal areas were nonpathologic with 324 patients in whom staging ranged from F0 to F3. Patients with cirrhosis (F4) were excluded from evaluation. To stage fibrosis, we used the METAVIR system. Furthermore, we selected 40 cases in which the biopsies measured at least 25 mm in length for further histochemical evaluation. Ten additional normal cases from our archives were used as controls. We divided this patient population into the following 5 groups of 10 patients each: group 1A, F0 with steatosis; group 1B, F0 without steatosis; group 2, F0 to F1, central injury; group 3, F3, fibrosis with multiple septa; and group 4, nonpathologic livers (controls).

Results.—Smooth muscle–specific α actin was expressed by stellate cells, pericentrally, with increasing severity and intensity in the advanced stage of fibrosis of group 3, less intense expression was noted in group 2, and expression was practically absent in group 1 and in nonpathologic controls. CD68 was the best marker for Kupffer cells and was expressed diffusely within the lobules in all groups. Its expression correlated directly with the degree of disease severity, progressing from stage I through stage III, but was absent in nonpathologic livers. CD34 was consistently expressed by endothelial cells in the periportal areas in all groups. The expression of collagen type 1 was intense in the bands of fibrosis or bridging, while type 3 expression was poor. Transforming growth factor β1 and intercellular adhesion molecule 1 were not expressed in any group.

Conclusions.—In this study, stellate cell activation (SMSA) was most intense pericentrally in the early stages and diffusely with progression to fibrosis and maximum intensity in stage III. Kupffer cell activation, as determined by CD68 expression, was intense and diffuse, while endothelial cells expressed CD34 periportally in a similar manner in all stages. Fibrogenesis in human ethanol injury is due to the activity of stellate cells, Kupffer cells, and to a lesser extent, to endothelial cells.

Role of NK and NKT cells in the immunopathogenesis of HCV-induced hepatitis

Natural killer (NK) cells constitute the first line of host defense against invading pathogens. They usually become activated in an early phase of a viral infection. Liver is particularly enriched in NK cells, which are activated by hepatotropic viruses such as hepatitis C virus (HCV). The activated NK cells play an essential role in recruiting virus-specific T cells and in inducing antiviral immunity in liver. They also eliminate virus-infected hepatocytes directly by cytolytic mechanisms and indirectly by secreting cytokines, which induce an antiviral state in host cells. Therefore, optimally activated NK cells are important in limiting viral replication in this organ. This notion is supported by the observations that interferon treatment is effective in HCV-infected persons in whom it increases NK cell activity. Not surprisingly, HCV has evolved multiple strategies to counter host's NK cell response. Compromised NK cell functions have been reported in chronic HCV-infected individuals. It is ironic that activated NK cells may also contribute toward liver injury. Further studies are needed to understand the role of these cells in host defense and in liver pathology in HCV infections. Recent advances in understanding NK cell biology have opened new avenues for boosting innate and adaptive antiviral immune responses in HCV-infected individuals.

An increased transforming growth factor beta receptor type I:type II ratio contributes to elevated collagen protein synthesis that is resistant to inhibition via a kinase-deficient transforming growth factor beta receptor type II in scleroderma

OBJECTIVE

Aberrant transforming growth factor beta (TGFbeta) signaling has been implicated in the pathogenesis of scleroderma (systemic sclerosis [SSc]), but the contribution of specific components in this pathway to SSc fibroblast phenotype remains unclear. This study was undertaken to delineate the role of TGFbeta receptor type I (TGFbetaRI) and TGFbetaRII in collagen overexpression by SSc fibroblasts.

METHODS

Primary dermal fibroblasts from SSc patients and healthy adults were studied (n = 10 matched pairs). Adenoviral vectors were generated for TGFbetaRI (AdTGFbetaRI), TGFbetaRII (AdTGFbetaRII), and kinase-deficient TGFbetaRII (AdDeltakRII). TGFbetaRI basal protein levels were analyzed by (35)S-methionine labeling/immunoprecipitation and immunohistochemistry. Type I collagen and TGFbetaRII basal protein levels were analyzed by Western blot and newly secreted collagen by (3)H-proline incorporation assay.

RESULTS

Analysis of endogenous TGFbetaRI and TGFbetaRII protein levels revealed that SSc TGFbetaRI levels were increased 1.7-fold (P = 0.008; n = 7) compared with levels in healthy controls, while TGFbetaRII levels were decreased by 30% (P = 0.03; n = 7). This increased TGFbetaRI:TGFbetaRII ratio correlated with SSc collagen overexpression. To determine the consequences of altered TGFbetaRI:TGFbetaRII ratio on collagen expression, healthy fibroblasts were transduced with AdTGFbetaRI or AdTGFbetaRII. Forced expression of TGFbetaRI in the range corresponding to elevated SSc TGFbetaRI levels increased basal collagen expression in a dose-dependent manner, while similar TGFbetaRII overexpression had no effect, although transduction of fibroblasts at higher multiplicities of infection led to a marked reduction of basal collagen levels. Blockade of TGFbeta signaling via AdDeltakRII resulted in approximately 50% inhibition of basal collagen levels in healthy fibroblasts and in 5 of 9 SSc cell lines. A subset of SSc fibroblasts (4 of 9 cell lines) was resistant to this treatment. SSc fibroblasts with the highest levels of TGFbetaRI were the least responsive to collagen inhibition via DeltakRII.

CONCLUSION

This study indicates that an increased TGFbetaRI:TGFbetaRII ratio may underlie aberrant TGFbeta signaling in SSc and contribute to elevated basal collagen production, which is insensitive to TGFbeta signaling blockade via DeltakRII.

Identification of transforming growth factors actively transcribed during the progress of liver fibrosis in biliary atresia

BACKGROUND/PURPOSE

Transforming growth factor-beta (TGF-beta) 1 and 2 and their receptors TbetaR-I, TbetaR-II, and TbetaR-III are powerful profibrogenic mediators in the body. Their expression has not been completely elucidated in the progress of liver fibrosis associated with biliary atresia (BA).

METHODS

The authors compared the cytokine expression in the liver of 3 patients with BA at Kasai's procedure (KP) and in 3 patients at liver transplantation (LT). Two liver samples from children with no liver disorders served as normal controls (CO). Real-time quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) was used to confirm the findings of relative mRNA expression of TGF-beta1 and 2 and their receptors. An immunohistochemistry and an enzyme-linked immunoassay (ELISA) were used to localize the liver cells that express TGF-beta2 and to quantitate the protein expression among groups.

RESULTS

Compared with controls, both TGF-beta1 and TGF-beta2 mRNA expression increased in the liver during the progress of liver fibrosis in patients with KP and LT on the array. Only TGF-beta2 showed a significant increase in expression in LT compared with KP and CO (P =.001 for TGF-beta2 and P = 0.054 for TGF-beta1). Both TbetaR-I and TbetaR-II showed no significant change among groups; TbetaR-III decreased significantly in LT compared with CO (P =.011). TGF-beta2 immunostaining was mainly localized in the bile duct epithelium and was remarkably higher in LT in which the proliferating bile ductules and the hepatocytes contributed to the increase in immunostaining and possibly to significantly higher plasma TGF-beta2 protein levels in LT than in KP.

CONCLUSIONS

This study identified TGF-beta2 as the most actively transcribed TGF-beta gene during the progress of liver fibrosis in BA and found a reciprocal relationship of upregulation of TGF-beta2 with downregulation of TbetaR-III in LT.

Thioacetamide-induced hepatic fibrosis in transforming growth factor beta-1 transgenic mice

OBJECTIVE

Transforming growth factor beta-1 (TGF-beta 1) is thought to be one of the most important factors affecting the development of fibrotic processes in the liver.

AIM

To discover whether endogenously higher TGF-beta 1 production influences the progression and reversibility of liver fibrosis in mice.

METHOD

We compared thioacetamide-induced liver fibrosis between wild-type and transgenic mice overexpressing active TGF-beta 1 in the liver. Hepatic fibrosis was detected on histological sections, and fibrotic areas were measured by means of morphometric analysis. We also performed Northern blot hybridisation and gelatine zymography to improve our understanding of the process.

RESULTS

The fibrotic process was faster in the transgenic animals, and regression after the withdrawal of the fibrogenic agent was slower. Fibrosis did not disappear completely from the TGF-beta 1 overexpressing mice, even at the endpoint of the experiment.

CONCLUSION

Since the increased TGF-beta 1 production in the liver slowed down the regression of the liver fibrosis, the behaviour of these transgenic mice is more similar to the human situation, where cirrhosis is irreversible. We propose that this transgenic model is more suitable for investigating fibrotic liver diseases than the experiments done previously on wild-type rodents.

Antagonistic effects of TNF-alpha on TGF-beta signaling through down-regulation of TGF-beta receptor type II in human dermal fibroblasts

Transforming growth factor-beta stimulates the production of the extracellular matrix, whereas TNF-alpha has antifibrotic activity. Understanding the molecular mechanism underlying the antagonistic activities of TNF-alpha against TGF-beta is critical in the context of tissue repair and maintenance of tissue homeostasis. In the present study, we demonstrated a novel mechanism by which TNF-alpha blocks TGF-beta-induced gene and signaling pathways in human dermal fibroblasts. We showed that TNF-alpha prevents TGF-beta-induced gene trans activation, such as alpha2(I) collagen or tissue inhibitor of metalloproteinases 1, and TGF-beta signaling pathways, such as Smad3, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinases, without inducing levels of inhibitory Smad7 in human dermal fibroblasts. TNF-alpha down-regulates the expression of type II TGF-beta receptor (TbetaRII) proteins, but not type I TGF-beta receptor (TbetaRI), in human dermal fibroblasts. However, neither TbetaRII mRNA nor TbetaRII promoter activity was decreased by TNF-alpha. TNF-alpha-mediated decrease of TbetaRII protein expression was not inhibited by the treatment of fibroblasts with either a selective inhibitor of I-kappaB-alpha phosphorylation, BAY 11-7082, or a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor, PD98059. Calpain inhibitor I (ALLN), a protease inhibitor, inhibits TNF-alpha-mediated down-regulation of TbetaRII. We found that TNF-alpha triggered down-regulation of TbetaRII, leading to desensitization of human dermal fibroblasts toward TGF-beta. Furthermore, these events seemed to cause a dramatic down-regulation of alpha2(I) collagen and tissue inhibitor of metalloproteinases 1 in systemic sclerosis fibroblasts. These results indicated that TNF-alpha impaired the response of the cells to TGF-beta by regulating the turnover of TbetaRII.

Inhibitory effect of a soluble transforming growth factor beta type II receptor on the activation of rat hepatic stellate cells in primary culture

BACKGROUND/AIMS

Oxidative stress, including the generation of reactive oxygen species (ROS) that acts as a signaling mediator for transforming growth factor (TGF)-beta, plays a key role in hepatic fibrosis. Hepatic stellate cells (HSCs) produce and respond to TGF-beta in an autocrine manner with increased collagen expression. It has previously been reported that the adenovirus-mediated overexpression of a soluble receptor against the extracellular domain of the TGF-beta type II receptor prevents hepatofibrogenesis in vivo, although its inhibitory role and mechanism in HSC activation remains to be elucidated.

METHODS

In this study, we report on an examination of the actual role of TGF-beta inhibition on oxidative stress and the activation of cultured rat HSCs, using the adenovirus-mediated soluble TGF-beta type II receptor.

RESULTS

This soluble receptor secreted from the adenovirus-infected cells binds to TGF-beta. Infection of HSCs with this adenovirus attenuated intracellular levels of TGF-beta1 mRNA and protein, NADH oxidative activity, ROS generation and lipid peroxidation, and prevented HSC activation.

CONCLUSIONS

These findings suggest that this adenovirus-mediated soluble TGF-beta receptor may lead to an interruption of the TGF-beta autocrine loop in activated HSC, in part, by inhibiting oxidative stress.

[Interstitial lung disease]

Molecular investigation into the physiopathology of interstitial lung diseases has gained special interest through the trials carried out in the last decade. These trials seem to point at the role played by certain molecules, such as cytokines (transforming growth factor, platelet derived growth factor) and integrins, in the processes that lead to pulmonary fibrosis during the course of interstitial lung disease. They also demonstrate the important role that angiotensin II plays in increasing the secretion of transforming growth factor by several cells. The above-mentioned studies allow new therapeutic approaches to be considered which will possibly improve the serious prognosis of such diseases once they have reached the last stage of their course: pulmonary fibrosis.