Molecular regulation of hepatic fibrogenesis

Effects of Portal Vein Arterialization on Regeneration and Morphology in Liver Transplantation: Investigations Using the Rat Model

BACKGROUND

Portal vein arterialization (PVA) has been proposed as a technical variant in liver transplantation in the case of non-recanalizable thrombosis. The present study investigates the effects of the arterialized portal vein on the function, morphology, and regenerative behavior of the liver.

METHODS

Different PVA techniques, including orthotopic liver transplantation, were used in a rat model. Portal blood flow was measured using a ultrasonic flowmeter. The regeneration capacity was determined on the basis of the increase of liver weight and the proliferating cell nuclear antigen index. The amount of hydroxyproline and the transcript levels of procollagen I were measured to determine the degree of fibrosis. The extracellular matrix was visualized with Picro-Sirius staining.

RESULTS

The measurements obtained with an ultrasonic probe revealed a significant increase in portal blood flow after PVA. The regeneration capacity in the groups after PVA with no flow reduction was comparable to that of the control. Liver transplantation and PVA with no flow reduction was followed by a significant increase (four- to sixfold) in the amount of hydroxyproline and the level of the mRNA for procollagen I. In the Picro-Sirius staining, periportal and perivascular fibrosis with incipient formation of septa was seen. After reduction of the portal blood flow, these effects were significantly less pronounced.

CONCLUSIONS

These operative techniques represent an excellent small animal model for studying the mechanism of liver regeneration and the genesis of fibrosis in liver and vessel tissue. The presenting findings indicate that the negative effects of "overarterialization" may be largely avoided by reducing portal blood flow. This implies that permanent PVA in clinical liver transplantation should be performed only in conjunction with a down-regulation of portal flow.

Interleukin-13 in the skin and interferon-gamma in the liver are key players in immune protection in human schistosomiasis

Immunity against schistosomes includes anti-infection immunity, which is mainly active against invading larvae in the skin, and anti-disease immunity, which controls abnormal fibrosis in tissues invaded by schistosome eggs. Anti-infection immunity is T-helper 2 (Th2) cell-dependent and is controlled by a major genetic locus that is located near the Th2 cytokine locus on chromosome 5q31-q33. Mutations in the gene encoding interleukin (IL)-13 that decrease or increase IL-13 production account, at least in part, for that genetic control. In contrast, protection against hepatic fibrosis is dependent on interferon (IFN)-gamma and is controlled by a major genetic locus that is located on 6q23, near the gene encoding the IFN-gamma receptor beta chain. Mutations that modulate IFN-gamma gene transcription are associated with different susceptibility to disease. These data indicate that IL-13 in the skin and IFN-gamma in the liver are key players in protective immunity against schistosomes. These roles relate to the high anti-fibrogenic activities of IFN-gamma and to the unique ability of IL-13 in Th2 priming in the skin and in the mobilization of eosinophils in tissues. The coexistence of strong IFN-gamma and IL-13-mediated immune responses in the same subject may involve the compartmentalization of the anti-schistosome immune response between the skin and the liver.

Blockage of transforming growth factor β receptors prevents progression of pig serum-induced rat liver fibrosis

AIM: To test the hypothesis that introduction of antisense TβR I and TβR II eukaryotic expressing plasmids into a rat model of immunologically induced liver fibrosis might block the action of TGF-β₁ and halt the progression of liver fibrosis.

METHODS: RT-Nest-PCR and gene recombination techniques were used to construct rat antisense TβR I and TβR II recombinant plasmids which could be expressed in eukaryotic cells. The recombinant plasmids and empty vector (pcDNA3) were encapsulated by glycosyl-poly-L-lysine and then transducted into rats of pig serum-induced liver fibrosis model. Expression of exogenously transfected gene was assessed by Northern blot, and hepatic expressions of TβR I and TβR II were evaluated by RT-PCR and Western blot.We also performed ELISA for serum TGF-β₁, hydroxyproline of hepatic tissues, immunohistoche-mistry for collagen types I and III, and VG staining for pathological study of the liver tissues.

RESULTS: The exogenous antisense TβR I and TβR II plasmids could be well expressed in vivo, and block mRNA and protein expression of TβR I and TβR II in the fibrotic liver at the level of mRNA respectively. These exogenous plasmid expressions reduced the level of TGF-β₁ (antisense TβR I group 23.998 ± 3.045 ng/mL, antisense TβR II group 23.156 ± 3.131 ng/mL, disease control group 32.960 ± 3.789 ng/mL; F = 38.19, 36.73, P < 0.01). Compared with disease control group, the contents of hepatic hydroxyproline (antisense TβR I group 0.169 ± 0.015 mg/g liver, antisense TβR II group 0.167 ± 0.009 mg/g liver, disease control group 0.296 ± 0.026 mg/g liver; F = 14.39, 15.48, P < 0.01) and the deposition of collagen types I and III decreased in the two antisense treatment groups (antisense TβR I group, collagen type I 669.90 ± 50.67, collagen type III 657.29 ± 49.48; antisense TβR II group, collagen type I 650.26 ± 51.51, collagen type III 661.58 ± 55.28; disease control group, collagen type I 1209.44 ± 116.60, collagen type III 1175.14 ± 121.44; F = 15.48 to 74.89, P < 0.01). Their expression also improved the pathologic classification of liver fibrosis models (compared with disease control group, χ² = 17.14, 17.24, P < 0.01). No difference was found in the level of TGF-β₁, the contents of hepatic hydroxyproline and collagen types I and III and pathologic grade between pcDNA3 control group and disease control group or between the two antisense treatment groups (F = 0.11 to 1.06, χ² = 0.13 to 0.16, P > 0.05).

CONCLUSION: Antisense TβR I and TβR II recombinant plasmids have certain reverse effects on liver fibrosis and can be used as possible candidates for gene therapy.

Amplified expression of dominant-negative transforming growth factor-beta type II receptor inhibits collagen type I production via reduced Smad-3 activity

BACKGROUND AND AIM

As a pleiotropic protein, transforming growth factor (TGF)-beta induces its effects by binding to its Ser/Thr kinase receptor type II and then recruiting and activating receptor type I, which is phosphorylated and activates Smads that transduce the signal to the nucleus.

METHODS

In this work, the authors blocked TGF-beta1 signal transduction pathway via delivery of a dominant-negative receptor-II (DeltaCyTbRII)-cDNA lacking Ser/Thr kinase intracytoplasmic domain activity. Thus, Cos-1 and hepatic stellate cells were cotransfected with pCMV5-DeltaCyTbRII and pAdTrack-green fluorescent protein using lipofectamine.

RESULTS

Fluorescence microscopy demonstrated an average 10% transfection efficiency. Radiolabeled 125I-TGF-beta was bound mostly by cell membrane-expressed truncated receptor-II rather than wild-type receptor type II. Electrophoretic mobility shift assays were performed using consensus Smad-2 and -3 sequences rendering a three-fold decrease in DNA-binding activity, reflecting a down-activation in Smad complexes in pCMV5-DeltaCyTbRII-transfected cells, but not in mock-transfected cells. The identity of these transcriptional factors was confirmed using irrelevant double-stranded oligonucleotides and specific antibodies to compete for DNA binding. Also, collagen I mRNA expression showed a five-fold decrease, which was reflected at the protein level as a diminished collagen type I production in pCMV5-DeltaCyTbRII-transfected Cos-1 cells as measured by [3H]proline incorporation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

CONCLUSION

Thus, this could be a useful strategy to downregulate or prevent exacerbated synthesis and deposition of extracellular matrix in a given fibrotic process.

Clinical, biochemical and imaging-verified regression of hepatitis B-induced cirrhosis

In a 65-year-old patient with ascites, jaundice and positive hepatitis B surface antigen (HBsAg), the histological diagnosis of cirrhosis with knodell total score 13 was made in 1995. The patient was followed up for 8 years. Spontaneous seroconversion of HBsAg appeared. Except for slight hyperbilirubinemia, all pathologic, clinical laboratory data remained normal from the second year of diagnosis till 8 years of follow-up. In the last follow up, the markers of liver fibrosis were all normal. The portal vein diameter was decreased and the esophageal varices disappeared. The imaging of liver by sonography and CT-scan did not reveal any abnormality.

Increased circulating and intrahepatic T-cell-specific chemokines in chronic hepatitis C: relationship with the type of virological response to peginterferon plus ribavirin combination therapy

AIMS

To determine the serum and intrahepatic levels of T-helper-1-associated chemokines in patients with chronic hepatitis C before, during and after peginterferon plus ribavirin combination therapy and to search for correlations with baseline characteristics of hepatitis C virus-related chronic liver disease and type of therapeutic response.

METHODS

Serum chemokine levels were determined by enzyme-linked immunosorbent assays and intrahepatic chemokine messenger RNA and protein levels were tested by ribonuclease protection assay and immunohistochemistry.

RESULTS

Serum and intrahepatic chemokine levels were elevated in all patients with chronic hepatitis C and showed a marked decrease in patients who obtained a virological response vs. non-responders. Increased serum interferon-gamma-inducible protein-10 levels at baseline in genotype 1-infected patients were significantly associated with greater degrees of intrahepatic inflammation and fibrosis (P = 0.0046 and P = 0.02, respectively) and with virological non-response (P = 0.01). In patients with genotype 1, basal serum interferon-gamma-inducible protein-10 levels greater than 299 pg/mL identified 80% of non-responders and lower than 299 pg/mL identified 63% of responders.

CONCLUSIONS

Circulating and intrahepatic T-helper-1-associated chemokines are abnormally elevated in patients with chronic hepatitis C. Increased baseline serum interferon-gamma-inducible protein-10 levels in genotype 1-infected patients are associated with virological non-response to peginterferon plus ribavirin combination therapy.

IFN-gamma polymorphisms (IFN-gamma +2109 and IFN-gamma +3810) are associated with severe hepatic fibrosis in human hepatic schistosomiasis (Schistosoma mansoni)

Schistosome infection is a major public health concern affecting millions of people living in tropical regions of Africa, Asia, and South America. Schistosomes cause mild clinical symptoms in most subjects, whereas a small proportion of individuals presents severe clinical disease (as periportal fibrosis (PPF)) that may lead to death. Severe PPF results from an abnormal deposition of extracellular matrix proteins in the periportal spaces due to a chronic inflammation triggered by eggs and schistosome Ags. Extracellular matrix protein production is regulated by a number of cytokines, including IFN-gamma. We have now screened putative polymorphic sites within this gene in a population living in an endemic area for Schistosoma mansoni. Two polymorphisms located in the third intron of the IFN-gamma gene are associated with PPF. The IFN-gamma +2109 A/G polymorphism is associated with a higher risk for developing PPF, whereas the IFN-gamma +3810 G/A polymorphism is associated with less PPF. The polymorphisms result in changes in nuclear protein interactions with the intronic regions of the gene, suggesting that they may modify IFN-gamma mRNA expression. These results are consistent with the results of previous studies. Indeed, PPF is controlled by a major locus located on chromosome 6q22-q23, closely linked to the gene encoding the alpha-chain of the IFN-gamma receptor, and low IFN-gamma producers have been shown to have an increased risk of severe PPF. Together, these observations support the view that IFN-gamma expression and subsequent signal transduction play a critical role in the control of PPF in human hepatic schistosome infection (S. mansoni).

Mechanical stretch induces TGF-beta synthesis in hepatic stellate cells

BACKGROUND

It is known that mechanical stress induces extracellular matrix via transforming growth factor-beta (TGF-beta) synthesis in vascular smooth muscle cells. Activated hepatic stellate cells (HSCs) are an important source of TGF-beta in the liver. However, it remains unclear whether mechanical stress induces TGF-beta in HSCs. The Rho small GTP-binding protein (Rho) has recently emerged as an important regulator of actin and cytoskeleton. We examined whether TGF-beta is expressed in stretched HSCs and whether Rho is involved in stretch-induced TGF-beta synthesis.

MATERIALS AND METHODS

A cultured human HSC cell line, LI90, was used for this study. Hepatic stellate cells were cyclically stretched using the Flexercell(R) strain unit. Concentration of TGF-beta in the conditioned medium was estimated by a bioassay using mink lung epithelial cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct. Transforming growth factor-beta mRNA expression of HSCs was estimated by a reverse-transcription polymerase chain reaction. Replication-defective adenoviral vectors expressing a dominant negative type of Rho was utilized to suppress its effect on HSCs.

RESULTS

Transforming growth factor-beta concentration of the conditioned media of stretched HSCs showed time-dependent increases as compared to nonstretched HSCs from 2 h to 24 h. Transforming growth factor-beta mRNA expression in stretched HSCs was increased compared with that in nonstretched HSCs. Transfection of dominant negative Rho inhibited the stretch-induced TGF-beta synthesis.

CONCLUSIONS

Mechanical stretch enhanced TGF-beta expression on mRNA and protein level in HSCs. Rho was closely related to stretch-induced TGF-beta synthesis in HSCs.

Cyclooxygenase 2 (COX2)-prostanoid pathway and liver diseases

Cycloocygenases 2 (COX2)-prostanoid pathway plays important and complex roles in the pathogenesis of various liver diseases. Most studies indicated that COX2-prostanoid pathway might suppress hepatic fibrogenesis by decreasing proliferation, migration, and contractility of hepatic stellate cells (HSCs). In animal model, COX2-prostanoid pathway increases portal hypertension, which can be reduced by treatment with COX2 inhibitor. In cirrhosis, COX2-prostanoid pathway may reduce formation of ascites by enhancing free water excretion, and protect gastric mucosa from ulcerative insults. Aberrant expression of COX2 has been well associated with hepatocarcinogenesis. COX2 inhibitors can effectively suppress proliferation of hepatocellular carcinoma (HCC) cells. This provided rationale for further testing COX2 inhibitors as clinical agents for HCC chemoprovention. Further studies will be needed to examine how COX2 inhibitors affect pathogenesis of various liver diseases.

Oxidative stress, KLF6 and transforming growth factor-beta up-regulation differentiate non-alcoholic steatohepatitis progressing to fibrosis from uncomplicated steatosis in rats

BACKGROUND/AIMS

Pathogenesis of non-alcoholic steatohepatitis (NASH) remains poorly understood. Cytochrome P450 2E1 (CYP 2E1), cytokines, oxidative stress and activation of hepatic stellate cells seem to play a role in this process. The aim was to determine the potential implication of these factors in the progression from uncomplicated steatosis to steatohepatitis with progressive fibrosis.

METHODS

Animals were fed a standard diet, a 5% orotic acid-diet (OA) developing hepatic steatosis, or the methionine-choline deficient (MCD) diet inducing steatohepatitis for 2 and 6 weeks. Lipid peroxidation, CYP 2E1 expression and activity, expression of UCP-2, interleukin (IL)-6, transforming growth factor (TGF)beta1, KLF6 mRNAs, and activation of hepatic stellate cells were examined by gas chromatography, high-performance liquid chromatography, Western blotting, quantitative polymerase chain reaction and immunohistochemistry.

RESULTS

Lipid peroxidation increased in the MCD model whereas only minor changes occurred in the OA model. KLF6 and TGFbeta1 mRNAs were selectively up-regulated in MCD animals. Stellate cell activation, inflammation and collagen deposition only occurred in the MCD group. CYP 2E1 expression and activity increased in the OA group while both decreased in MCD animals. UCP-2 and IL-6 mRNA increased in both groups.

CONCLUSIONS

In the context of steatosis, lipid peroxidation is associated with inflammation and stellate cell activation with concomitant increase in TGFbeta1 production, possibly through up-regulation of KLF6.

Altered expression of genes involved in hepatic morphogenesis and fibrogenesis are identified by cDNA microarray analysis in biliary atresia

Biliary atresia (BA) is characterized by a progressive, sclerosing, inflammatory process that leads to cirrhosis in infancy. Although it is the most common indication for liver transplantation in early childhood, little is known about its etiopathogenesis. To elucidate factors involved in this process, we performed comprehensive genome-wide gene expression analysis using complementary DNA (cDNA) microarrays. We compared messenger RNA expression levels of approximately 18,000 human genes from normal, diseased control, and end-stage BA livers. Reverse-transcription polymerase chain reaction (RT-PCR) and Northern blot analysis were performed to confirm changes in gene expression. Cluster and principal component analysis showed that all BA samples clustered together, forming a distinct group well separated from normal and diseased controls. We further identified 35 genes and ESTs whose expression differentiated BA from normal and diseased controls. Most of these genes are known to be associated with cell signaling, transcription regulation, hepatic development, morphogenesis, and fibrogenesis. In conclusion, this study serves to delineate processes that are involved in the pathogenesis of BA.

Preparation and identification of anti-transforming growth factor β1 U1 small nuclear RNA chimeric ribozyme in vitro

AIM: To study the preparation and cleavage activity of anti-transforming growth factor (TGF)β1 U1 small nuclear (sn) RNA chimeric hammerhead ribozymes in vitro.

METHODS: TGFβ1 partial gene fragment was cloned into T-vector at the downstream of T7 promoter. ³²p-labeled TGFβ1 partial transcripts as target RNA were transcribed in vitro and purified by denaturing polyacrylamide gel electrophoresis (PAGE). Anti-TGFβ1 ribozymes were designed by computer, then synthetic ribozyme fragments were cloned into the U1 ribozyme vector pZeoU1EcoSpe containing U1 snRNA promoter/enhancer and terminator. ³²p-labeled U1 snRNA chimeric ribozyme transcripts were gel-purified, incubated with target-RNAs at different conditions and autoradiographed after running denaturing PAGE.

RESULTS: Active U1snRNA chimeric ribozyme (U1Rz803) had the best cleavage activity at 50 °C; at 37 °C, it was active, K_m = 34.48 nmol/L, K_cat = 0.14 min^-1; while the point mutant ribozyme U1Rz803_m had no cleavage activity, so these indicated the design of U1Rz803 was correct.

CONCLUSION: U1Rz803 prepared in this study possessed the perfect specific catalytic cleavage activity. These results indicate U1 snRNA chimeric ribozyme U1Rz803 may suppress the expression of TGFβ1 in vivo, therefore it may provide a new avenue for the treatment of liver fibrosis in the future.

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Oxidative-stress-related changes in the livers of bile-duct-ligated rats

The role of reactive oxygen species in liver fibrogenesis is not yet clarified. The aim of this study was to investigate oxidative-stress-related changes in cirrhotic rats. Cirrhosis was induced by bile duct ligation in Sprague-Dawley rats. Plasma malondialdehyde (MDA), hepatic 8-hydroxy-2'-deoxyguanosine (8-OHdG), hepatic mitochondrial respiratory functions and gene transcripts were measured at 2 and 4 weeks after surgery in bile-duct-ligated (BDL) and sham-operated-operated rats. The results showed progressive increases in the levels of plasma MDA, hepatic 8-OHdG and procollagen I and III mRNA expression, and progressive impairment of hepatic mitochondrial respiratory function in BDL rats at 2 and 4 weeks after ligation compared with sham-operated rats. Moreover, at 4 weeks after ligation, BDL rats exhibited reduced plasma glutathione and vitamin E levels, impaired hepatic mitochondrial electron transport enzyme activities and oxidative phosphorylation function. In addition, hepatic mRNA expression of transforming growth factor-beta1 was increased. Hepatomegaly, abnormal plasma alanine transaminase and aspartate transaminase levels, and portal hypertension were noted in BDL rats. Our results suggest that bile duct ligation in the rat induces mitochondrial dysfunction and biochemical and molecular changes related to oxidative stress in the liver.

Changes in serum cytokine concentration: a morphological study of liver cirrhosis induced by common bile duct ligation in rats

BACKGROUND

Liver cirrhosis is a diffuse hepatic fibrosis, and nodule formation. The transforming growth factor-beta 1 (TGF-beta 1) and interleukin-10 (IL-10) are very important cytokines in hepatic fibrogenesis. The aim of this study was to examine the relationship between the changes of the serum cytokines and morphological changes following common bile duct ligation in experimental rats.

METHODS

Common bile ducts of fifty male Sprague-Dawley rats were ligated and seven male rats were set aside as controls. Five rats each were sacrificed in 1, 2, 4, 6, 8, and 10 experimental weeks. Light microscopic studies and liver function tests were performed during the above experimental weeks. The levels of serum TGF-beta 1 and IL-10 were analyzed by ELISA. Also, alpha smooth muscle actin (alpha-SMA) immunohistochemical stains were performed.

RESULTS

On the eighth week after common bile duct ligation, most hepatic lobular areas had been replaced by proliferated bile ducts and fibrous tissue (typical biliary cirrhosis). Serum TGF-beta 1 levels between the control group and the common bile duct ligation group showed statistically significant changes. The alpha-SMA was stained at proliferated bile ducts. These findings were correlated with each other.

CONCLUSION

Thus, this experiment may clarify our understanding of the mechanism in liver fibrogenesis. Also, indicated is a need to explore the therapeutic potential of these cytokines as anti-fibrotic agents.

Expression of TIMP-1 in normal and fibrotic livers in rats

AIM: To investigate the expression of TIMP-1 in normal and experimental fibrotic livers in rats.

METHODS: Hepatic fibrosis rat models were induced with human serum albumin, and normal rats were used as control. TIMP-1 mRNA and its related antigens in liver were examined with immunohistochemistry and in situ hybridization. Expression of TIMP-1 gene was detected with PCR.

RESULTS: The positive signal of TIMP-1 proteins was mainly located in cytoplasm rather than nucleus in hepatic myofibroblasts and fibroblasts, which dominated in portal areas and fibrous septums fibrotic rats. Such distribution of expression of TIMP-1 detected with immunohistochemistry was consistent with that in situ hybridization. The level of TIMP-1 expression in fibrotic rats was obviously higher than that in normal ones.

CONCLUSION: TIMP-1 was expressed dominantly in fibroblast and myofibroblast in fibrotic liver, the expression level increased with progression of liver injury and severity of hepatic fibrosis.

Inhibition on the production of collagen type I, III of activated hepatic stellate cells by antisense TIMP-1 recombinant plasmid

AIM

To investigate the inhibition effects on the production of collagen type I, III secreted by activated rat hepatic stellate cells (rHSCs) by antisense tissue inhibitors of metalloproteinase 1 (TIMP-1) recombinant plasmid through elevating interstitial collagenase activity.

METHODS

rHSCs were extracted from normal rat liver by pronase and collagenase digestion and purified by centrifugal elutriation, and were cultured on plastic dishes until they were activated to a myofibroblastic phenotype after 7-10 days. RT-Nest-PCR and gene recombinant techniques were used to construct the rat antisense TIMP-1 recombinant plasmids which can express in eucaryotic cells. The recombinant plasmid and the pcDNA3 empty plasmid were transfected in rHSCs by Effectene (QIAGEN) separately. Cells were selected after growing in DMEM containing 400 microg/ml G418 for 2-3 weeks. Expression of exogenous gene was assessed by Northern blot, and expression of TIMP-1 in rHSCs was determined by Northern blot and Western blot. We tested the interstitial collagenase activity with FITC-labled type I collagen as substrate. Ultimately, we quantified the type I, III collagen by Western blot.

RESULTS

The exogenous antisense TIMP-1 recombinant plasmid could be expressed in rHSCs well, which could block the expression of TIMP-1 greatly, the ratio of TIMP-1/GAPDH was 0.67, 2.41, and 2.97 separately at mRNA level (P<0.05); the ratio of TIMP-1/beta-actin was 0.31, 0.98 and 1.32 separately at protein level (P<0.05); It might elevate active and latent interstitial collagenase activity, the collagenase activity was 0.3049, 0.1411 and 0.1196 respectively. (P<0.05), which led to promotion the degradation of type I, III collagen, the ratio of collagen I/beta-actin was 0.63, 1.78 and 1.92 separately (P<0.05); and the ratio of collagen III/beta-actin was 0.59, 1.81 and 1.98 separately (P<0.05).

CONCLUSION

These data shows that the antisense TIMP-1 recombinant plasmid has the inhibitory effects on the production of type I, III collagens secreted by activated rHSCs in vitro. It could be a novel method to reverse hepatic fibrosis in the future.

Gadolinium chloride reverses dimethylnitrosamine (DMN)-induced rat liver fibrosis with increased matrix metalloproteinases (MMPs) of Kupffer cells

The aim of this study was to investigate whether matrix metalloproteinases (MMP-13, 9) of Kupffer cells induced by gadolinium chloride (GdCl(3)) treatment can reverse dimethylnitrosamine (DMN)-induced liver fibrosis (in vivo) and the effect of GdCl(3) on MAP kinase activity (in vitro). Male Wistar rats 6 weeks of age received DMN (10 mg/kg) three successive days a week for 4 weeks. Then two groups of rats (n = 6 each) were treated twice weekly with either GdCl(3) (7 mg/kg) or saline solution intravenously for the next 4 weeks. Animals were sacrificed to estimate the degree of liver fibrosis. Isolated Kuppfer cells were treated with GdCl(3) and the expressions of MMPs, MAP kinase activity (ERK, SAPK/JNK, P38) as well as apoptosis were also examined. Rats that received DMN for 4 weeks followed by GdCl(3) injection for 4 weeks showed an reduced liver hydroxyproline content compared to rats treated with DEN followed by saline (277 +/- 22 VS 348 +/- 34 microg/g, n = 6 each, P < 0.01). There were significantly increased MMP-13 mRNA levels in GdCl(3)-treated rats. However, no significant change was observed in procollagen type I mRNA levels. Isolated Kuppfer cells treated with GdCl(3) showed increased MAP kinase activity, especially P38 pathway as well as MMP-13, 9 mRNA and type I collagen-degrading activity leading to apoptosis. SB203580, inhibitor of P38 pathway diminished these activation and prevented apoptosis. These results suggest that Kuppfer cells can reverse liver fibrosis via the expression of MMPs mainly through P38 pathway.

Liver fibrosis: insights into migration of hepatic stellate cells in response to extracellular matrix and growth factors

BACKGROUND & AIMS

In liver fibrosis, alterations within the space of Disse microenvironment occur and facilitate further progression of chronic liver disease. The normal basement membrane-like matrix present within the space of Disse converts to a matrix rich in fibril-forming collagens during fibrosis.

METHODS

To further understand the pathogenesis of liver fibrosis, we modified an in vitro Boyden chamber system to partially mimic in vivo conditions of hepatic stellate cells (HSCs) during health and disease.

RESULTS

Stimulation of HSCs with platelet-derived growth factor (PDGF)-BB, transforming growth factor (TGF)-beta1, and/or epithelial growth factor (EGF) resulted in an increase in their migratory capacity and up-regulated matrix metalloproteinase (MMP)-2 activity. Migration induced by PDGF-BB was associated with increased proliferation, whereas TGF-beta1/EGF-induced migration was proliferation independent. COL-3, an inhibitor of MMP-2 and MMP-9, inhibited migration of HSCs induced by direct activation of PDGF-BB or TGF-beta1 but had no effect on migration induced by chemotactic stimuli without direct contact, suggesting 2 distinct MMP-dependent and MMP-independent mechanisms of PDGF-BB- or TGF-beta1-induced migration. Additionally, we show that type I collagen by itself induced migration of HSCs. Migration induced by PDGF-BB, TGF-beta1, and collagen I could be inhibited by alpha(1)- and/or alpha(2)-integrin blocking antibodies, collectively suggesting an integrin-dependent, MMP-2-mediated migration of HSCs.

CONCLUSIONS

Basement membrane matrix integrity, composition, and cell-matrix interactions play an important role in anchoring HSCs and preventing them from spreading within the space of Disse and potentially elsewhere in the liver. Additionally, our data provide strong evidence for MMPs in regulation of HSCs migration.

Transcriptional activation of endoglin and transforming growth factor-beta signaling components by cooperative interaction between Sp1 and KLF6: their potential role in the response to vascular injury

Endoglin is an endothelial membrane glycoprotein involved in cardiovascular morphogenesis and vascular remodeling. It associates with transforming growth factor-beta (TGF-beta) signaling receptors to bind TGF-beta family members, forming a functional receptor complex. Arterial injury leads to up-regulation of endoglin, but the underlying regulatory events are unknown. The transcription factor KLF6, an immediate-early response gene induced in endothelial cells during vascular injury, transactivates TGF-beta, TGF-beta signaling receptors, and TGF-beta-stimulated genes. KLF6 and, subsequently, endoglin were colocalized to vascular endothelium (ie, expressed in the same cell type) following carotid balloon injury in rats. After endothelial denudation, KLF6 was induced and translocated to the nucleus; this was followed 6 hours later by increased endoglin expression. Transient overexpression of KLF6, but not Egr-1, stimulated endogenous endoglin mRNA and transactivated the endoglin promoter. This transactivation was dependent on a GC-rich tract required for basal activity of the endoglin promoter driven by the related GC box binding protein, Sp1. In cells lacking Sp1 and KLF6, transfected KLF6 and Sp1 cooperatively transactivated the endoglin promoter and those of collagen alpha1(I), urokinase-type plasminogen activator, TGF-beta1, and TGF-beta receptor type 1. Direct physical interaction between Sp1 and KLF6 was documented by coimmunoprecipitation, pull-down experiments, and the GAL4 one-hybrid system, mapping the KLF6 interaction to the C-terminal domain of Sp1. These data provide evidence that injury-induced KLF6 and preexisting Sp1 may cooperate in regulating the expression of endoglin and related members of the TGF-beta signaling complex in vascular repair.

Emerging concepts in inflammation and fibrosis

Hepatic and pancreatic response to several insults commonly includes similar pathways of inflammation, fibrogenesis/regeneration, which may occur simultaneously and without appropriate coordination, resulting in chronic inflammation, scarring, and organ dysfunction. This review highlights the opinion of experts gathered for the Mexican Digestive Disease Week (2001) to analyze these molecular events with emphasis on identifying possible therapeutic opportunities. Inflammatory response encompasses leukocyte infiltration, favored by adhesion molecules of the selectin family, chemokines, integrins, and activated stellate cells (SC). Quiescent SC undergo activation mediated by mechanical stress and expression of cytokines, oxidative stress products, and growth factors and play a significant role in fibrosis and in reparation toward synthesis of extracellular matrix components. Also, hepatocytes and acinar cells contribute to the inflammatory and fibrotic response. Molecules that down-regulate this response are overexpressed. Therapeutic strategies with targeting to such mechanisms underlying chronic hepatic and pancreatic injury are an emerging reality.

Tissue inhibitor of metalloproteinases-1 attenuates spontaneous liver fibrosis resolution in the transgenic mouse

It has been suggested that the tissue inhibitor of metalloproteinases-1 (TIMP-1) is involved in spontaneous resolution of liver fibrosis. The aim of this study was to investigate whether TIMP-1 altered spontaneous resolution of liver fibrosis in conjunction with matrix metalloproteinases (MMP) inhibition and hepatic stellate cell (HSC) activation. The livers of liver-targeted TIMP-1 transgenic (TIMP-Tg) and control hybrid (Cont) mice were harvested at 0, 3, 7, and 28 days following spontaneous recovery from CCl(4)-induced liver fibrosis. The extent of fibrosis resolution, MMP expression, alpha-smooth-muscle actin (alpha-SMA) positive cells, and procollagen-(I) messenger RNA (mRNA) in the liver were assessed at the respective periods in both groups. We also examined the effect of TIMP-1 on HSC apoptosis. The TIMP-Tg mice showed significantly attenuated resolution of spontaneous liver fibrosis compared with the Cont mice. The hydroxyproline content, number of alpha-SMA positive cells, and procollagen-(I) mRNA rapidly decreased with time in the Cont mice, whereas these markers were little changed in TIMP-Tg mice. The level of the active form of metalloproteinases-2 (MMP-2) in the TIMP-Tg mice was less than that in the Cont mice. TIMP-1 markedly decreased the nonparenchyma apoptotic cells in the liver fibrosis resolution model, and it also inhibited HSC apoptosis associated with suppression of caspase-3 activity in vitro. In conclusion, TIMP-1 significantly attenuated spontaneous resolution of liver fibrosis by the combination of a net reduction of the MMP activity and suppression of apoptosis in HSC.

PAV-1, a new rat hepatic stellate cell line converts retinol into retinoic acid, a process altered by ethanol

During liver fibrogenesis or long term culture, hepatic stellate cells (HSCs) evolved from "quiescent" to activated phenotype called "myofibroblast-like", a transition prevented by retinoic acid (RA). Little is known about RA generation by HSCs. Our study aimed to check the ability of these cells to produce RA from retinol (Rol) and the alterations of this metabolic step by ethanol. To study this metabolic pathway, primary cultures of HSCs represent the most physiological model but technically suffer several drawbacks. To circumvent these problems, an immortalized rat HSC line (named PAV-1) has been established. We validated PAV-1 cell line as a convenient model to study retinoids metabolism by HSCs. Then, we showed that PAV-1 cells express Rol-binding proteins (RBPs), enzymes and nuclear receptors involved in RA signaling pathway. We also demonstrated in situ generation of functional all-trans-RA (ATRA), using transient transfections with a RA-sensitive reporter gene, in situ modulation of tissue transglutaminase (tTG) activity and HPLC experiments. This production was Rol dose-dependent; 4-methylpyrazole, citral, and ethanol-inhibited which argues in favor of an enzymatic process.In conclusion, we first demonstrate in situ RA generation from Rol in a newly immortalized rat HSC line, named PAV-1. Inhibition of RA production by ethanol in PAV-1 and recent data, suggesting fundamental role of RA to prevent fibrosis development in the liver, allow us to hypothesize that Rol metabolism could be a primary target for ethanol during development of hepatic fibrosis.

Mesenchymal cells in the liver--one cell type or two?

The wall of the liver sinusoid is made of highly specialized cells, the hepatic stellate cells (HSC) which together with the sinusoidal endothelial cells represent a loose barrier to the corpusculate part of the blood flowing through the liver. Quiescent stellate cells (quiescent HSC) store Vitamin A; "activated" stellate cells become involved in the reaction to acute or chronic noxae damaging the liver parenchyma. Activated HSC show increased protein synthesis capacity, increased DNA-synthesis and acquire a myofibroblast-like phenotype. Under similar conditions liver myofibroblasts (MF) of the portal field and of the pericentral area may also become "activated" by increasing protein synthesis, DNA synthesis and cell division. They express the fibulin-2 gene and produce large amounts of IL-6. In contrast to "activated" HSC they do not undergo spontaneous apoptosis in vitro and do not express the CD95-ligand gene. So far no definite prove has been found for a "transdifferentiation" of HSC to myofibroblasts. On the contrary an increasing amount of data support the conviction that HSC and MF represent two similar but not identical cell populations the latter being comparable to those of other organs.

Quantitative monitoring of the mRNA expression pattern of the TGF-beta-isoforms (beta 1, beta 2, beta 3) during transdifferentiation of hepatic stellate cells using a newly developed real-time SYBR Green PCR

Current methods to determine the mRNA of the TGF-beta-isoforms, beta 1, beta 2, and beta 3, are not sensitive enough to detect small alterations in the expression levels. Therefore, we established a SYBR Green I-based real-time quantitative PCR procedure with fragment-specific standards. The advantage of gene-specific quantification is the possibility to be abstain from the need to compare results with a house-keeping gene having a different sequence and PCR efficiency. Reproducibility of the results and analytical variances of the real-time PCR assays were tested. In transdifferentiating rat hepatic stellate cells (HSC) the TGF-beta 1-mRNA was found to be the predominant isoform expressed followed by TGF-beta 3 and low amounts of TGF-beta 2-mRNA. An alteration of the TGF-beta 1,-beta 2, and -beta 3 ratio during HSC transdifferentiation could not be detected. Furthermore, the GAPDH mRNA expression varied during HSC activation, and thus is not recommended as a standard in real-time PCR quantifications.

Antidiabetic thiazolidinediones inhibit collagen synthesis and hepatic stellate cell activation in vivo and in vitro

BACKGROUND & AIMS

The ligand-dependent transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is expressed in hepatic stellate cells (HSC), and its transcriptional activity is reduced during cell transdifferentiation in culture. PPARgamma transcriptional activation decreases platelet-derived growth factor-induced proliferation and inhibits alpha-smooth muscle actin expression in cultured HSC. The aim of our study was to evaluate whether oral administration of synthetic PPARgamma ligands, thiazolidinediones (TZD), might affect collagen deposition in animal models of liver fibrosis.

METHODS

The effect of 2 TZD (pioglitazone or rosiglitazone) was tested on liver fibrosis induced in rats by either toxin administration (dimethylnitrosamine or carbon tetrachloride) or bile duct ligation. In vivo PPARgamma activation was evaluated by gel shift assay using nuclear extracts from HSC isolated from control and treated rats.

RESULTS

Oral administration of TZD reduced extracellular matrix deposition and HSC activation in both toxic and cholestatic models of liver fibrosis. PPARgamma-specific DNA binding was significantly impaired in nuclear extracts of HSC isolated from fibrotic rats compared with HSC from control rats. TZD administration restored PPARgamma DNA binding in HSC nuclei. In vitro, TZD-induced PPARgamma activation inhibited collagen and fibronectin synthesis induced by transforming growth factor (TGF)-beta1 in human HSC, as measured by enzyme-linked immunosorbent assay and Northen blotting. TZD also reduced the TGF-beta1-induced activity of a 3.5-kilobase procollagen type I promoter transfected in human HSC.

CONCLUSIONS

These findings indicate that PPARgamma activation in HSC retards fibrosis in vivo and suggest the use of TZD for the treatment of liver fibrosis.

Neutrophil migration during liver cirrhosis in rabbits

1. The aim of the present study was to investigate neutrophil chemotaxis during the induction of liver cirrhosis in rabbits. 2. Liver cirrhosis was induced in male New Zealand white rabbits. The study consisted of three experimental groups: (i) group A (n=16) served as the control and received only normal chow and all rabbits in this group were killed at 16 weeks; (ii) group B rabbits (n=8) were killed immediately after the chemotaxis assay, which was performed 24 h after CCl4 administration, at weeks 2, 4, 6 and 8; and (iii) in group C rabbits (n=19), the chemotaxis assay was performed every second week on the day before CCl4 administration for 16 weeks and all animals in this group were killed at 16 weeks. 3. Four of six rabbits in group B had liver cirrhosis at week 8. In group C, liver cirrhosis occurred in seven of eight animals. All rabbits with liver cirrhosis had an inflammatory infiltrate of neutrophils. In group B, there was a significant increase in polymorphonuclear cells and neutrophil chemotaxis and a significant reduction in mononuclear leucocytes at week 8. The rabbits in group C showed a significant increase in total leucocyte and polymorphonuclear numbers at week 10. A significant increase in neutrophil chemotaxis was also observed from week 2 through to week 6. 4. The presence of neutrophils in the liver of all rabbits with cirrhosis, associated with an increase in polymorphonuclear cell chemotaxis during this process, supports the view that this cell type has an important role in the development of toxic liver damage.

Methodologic research on TIMP-1, TIMP-2 detection as a new diagnostic index for hepatic fibrosis and its significance

AIM

To set up a new method to detect tissue inhibitors of metalloproteinase-1 and -2(TIMP-1 and TIMP-2) in sera of patients with hepatic cirrhosis, and to investigate the expression and location of TIMP-1 and TIMP-2 in liver tissue of patients with hepatic cirrhosis, and the correlation between TIMPs in liver and those in sera so as to discuss whether TIMPs can be used as a diagnosis index of hepatic fibrosis.

METHODS

The monoclonal antibodies (McAbs) of TIMP-1 and TIMP-2 were used to sensitize erythrocytes, and solid-phase absorption to sensitized erythrocytes (SPASE) was used to detect TIMP-1 and TIMP-2 in the sera of patients with hepatic cirrhosis. Meanwhile, with the method of in situ hybridization and immunohistochemistry, we studied the mRNA expression and antigen location of TIMP-1 and TIMP-2 in the livers of 40 hepatic cirrhosis patients with pathologic diagnosis.

RESULTS

With SPASE, they were 16.4% higher in the acute hepatitis group, 33.3% higher in the chronic hepatitis group, and the positive rates were 73.6% and 61.2% respectively in sera of hepatic cirrhosis patients, which were remarkably higher than those in chronic hepatitis and acute hepatitis group (P<0.001). In 40 samples of hepatic cirrhosis tissues, all of them showed positive expression of TIMP-1 and TIMP-2 mRNA detected with immunohistochemistry or in situ hybridization (positive rate was 100%). Expression of TIMPs in different degrees could be found in liver tissue with cirrhosis. TIMPs were located in cytoplasm of liver cells of patients with hepatic cirrhosis. There was a significant correlation between serum TIMPs level and liver TIMPs level.

CONCLUSION

SPASE is a useful method to detect the TIMP-1 and TIMP-2 in sera of patients with hepatic cirrhosis, and TIMP-1 and TIMP-2 can be considered as a useful diagnostic index of hepatic fibrosis, especially TIMP-1.

Inhibition of hepatic stellate cell collagen synthesis by N-(methylamino)isobutyric acid

The increased deposition of extracellular matrix by hepatic stellate cells following liver injury, in a process known as activation, is considered a key mechanism for increased collagen content of liver during the development of liver fibrosis. We report that N-(methylamino)isobutyric acid (MeAIB), a specific inhibitor of System A-mediated amino acid uptake, reduces the accumulation of collagen in CFSC-2G hepatic stellate cell cultures and in a rat model of liver injury and fibrosis. Rat CFSC-2G cells were cultured in 0-5mM MeAIB, and the accumulation and synthesis of collagen were measured by binding to Sirius red F3B and pulse-labeling with [3H]-proline, respectively. The effect of MeAIB on collagen accumulation in vivo was evaluated utilizing a rat model of hepatic fibrosis. MeAIB inhibited collagen accumulation in CFSC-2G cultures in a concentration-dependent manner with 5mM MeAIB reducing collagen 44.6+/-1.2% compared with the control. In CFSC-2G cultures, MeAIB selectively inhibited the incorporation of proline into cellular macromolecules by 43+/-4%, while the synthesis of proteins containing leucine was not affected. In vivo, oral administration of 160mg MeAIB/kg body weight per day to rats significantly reduced the hepatic collagen accumulation in response to 1 week of CCl(4)-induced liver injury. MeAIB reduces the accumulation of collagen in CFSC-2G hepatic stellate cell cultures and in a CCl(4)-induced rat model of liver injury and fibrosis.

Oncostatin M stimulates tissue inhibitor of metalloproteinase-1 via a MEK-sensitive mechanism in human myofibroblasts

BACKGROUND/AIMS

We previously showed that in cultured human myofibroblasts (hMFBs), Oncostatin M (OSM)-stimulated collagen accumulation is associated with increased tissue inhibitor of metalloproteinase (TIMP)1 message. However, the mechanism is unknown.

METHODS

hMFBs were isolated by outgrowth from cirrhotic liver explants and cultured. Using OSM (10 ng/ml) stimulation, with and without PD98059 (PD, a specific mitogen-activated protein kinase/extracellular signal-related kinase (MEK) inhibitor), we measured: TIMP-1 protein in culture medium by Western blot, TIMP-1 mRNA levels and stability by Northern analysis, TIMP-1 promoter activity (including transcription site mutation analysis), DNA binding activity to nuclear proteins by electrophoretic mobility shift assay (EMSA), and total and phosphorylated MAP kinase in hMFB extracts by Western blot.

RESULTS

OSM stimulation of hMFBs increased TIMP-1 protein production 1.69-fold, TIMP-1 mRNA levels 2.36-fold, promoter activity 2.22-fold, TIMP-1 message stability, and phosphorylation of mitogen-activated protein kinase (MAPK). PD inhibited OSM-mediated stimulation of TIMP-1 protein, mRNA, promoter activity, phosphorylation of MAPK, and TIMP-1 message stability. An SP-1 transcription site of the TIMP-1 promoter is essential for OSM induction of TIMP-1 promoter activity. EMSA demonstrates that this site binds to transcriptional factors SP-1 and SP-3.

CONCLUSIONS

OSM stimulates the TIMP-1 axis in hMFBs in vitro via a MEK-MAP kinase cascade.

Delayed liver regeneration with negative regulation of hepatocyte growth factor and positive regulation of transforming growth factor-beta1 mRNA after portal branch ligation in biliary obstructed rats

BACKGROUND

The influence of obstructive jaundice on liver regeneration is still controversial. The aim of this study was to investigate liver regeneration after portal branch ligation (PBL) in the jaundiced rat, focusing on hepatocyte growth factor (HGF) and transforming growth factor-beta1 (TGF-beta 1).

METHODS

Male Wistar rats underwent PBL or a sham operation 7 days after a common bile duct ligation. Liver wet weight, proliferating cell nuclear antigen labeling, HGF and TGF-beta 1 mRNA expression, and immunohistochemical staining with alpha-smooth muscle actin antibody were studied.

RESULTS

The rate of liver regeneration in jaundiced liver was decreased as compared to a non-jaundiced liver. DNA synthesis in the jaundiced non-ligated lobe was significantly lower than in the non-jaundiced liver as was the peak level of HGF mRNA expression after PBL. In contrast, the level of TGF-beta 1 mRNA expression was higher in the jaundiced liver, and alpha-smooth muscle actin staining showed that hepatic stellate cells were gradually activated into myofibroblast-like cells.

CONCLUSIONS

Obstructive jaundice decreased the expression of HGF mRNA and increased the expression of TGF-beta 1 mRNA, resulting in delayed liver regeneration after PBL. We suggest that hepatic stellate cells activated in obstructive jaundice may affect the expression of these growth factors.

Rearrangement of the cytoskeletal network induced by platelet-derived growth factor in rat hepatic stellate cells: role of different intracellular signalling pathways

BACKGROUND/AIMS

Cytoskeletal reorganization plays an important role in the regulation of different cell functions, such as proliferation and migration. Since platelet-derived growth factor (PDGF) stimulates both proliferation and chemotaxis of hepatic stellate cells (HSC), we investigated the effects of this cytokine on cytoskeletal components of cultured rat HSC.

METHODS/RESULTS

Exposure of HSC to PDGF induced the formation of stress fibres and of a ruffled configuration of the plasma membrane, evaluated by both fluorescence and electron microscopy. These modifications were also induced by exposure to the protein kinase C (PKC) activator phorbol-12-myristate-13-acetate (PMA) and abolished by pretreatment with the PKC inhibitor calphostin C, with the Rho inhibitor C3 exoenzyme and with the intracellular calcium chelator MAPTAM, but not with the PI-3 kinase inhibitor wortmannin or with the mitogen-activated protein kinase kinase inhibitor PD 98059. PDGF induced a translocation of Rho from the cytosol to the membrane which was inhibited by C3 exoenzyme and by calpostin C, and which was also induced by PMA. Moreover, PDGF induced a rearrangement of vinculin which was prevented by C3 exoenzyme and calphostin C.

CONCLUSIONS

PDGF-induced cytoskeletal reorganization in HSC is dependent on PKC and Rho, thus suggesting that these two pathways may play an important role in the response of liver to injury.

Cirrhotic rat livers with extensive fibrosis can be safely transduced with clinical-grade adenoviral vectors. Evidence of cirrhosis reversion

Adenoviral vectors efficiently target normal liver cells; however, a clear-cut description of the safety boundaries for using adenovectors in hepatic cirrhosis has not been settled. With this in mind, we used a first-generation, replication-deficient adenoviral vector carrying the E. coli lacZ gene (Ad5betaGal) to monitor therapeutic range, biodistribution, toxicity and transduction efficiency in Wistar rats made cirrhotic by two different experimental approaches resembling alcoholic cirrhosis and biliary cirrhosis in humans. Further, we show proof of concept on fibrosis reversion by a 'therapeutic' Ad-vector (AdMMP8) carrying a gene coding for a collagen-degrading enzyme. Dose-response experiments with Ad5betaGal ranging from 1 x 10(8)-3 x 10(12) viral particles (vp) per rat (250 g), demonstrated that adenovirus-mediated gene transfer via iliac vein at 3 x 10(11 )vp/rat, resulted in an approximately 40% transduction in livers of rats made cirrhotic by chronic intoxication with carbon tetrachloride, compared with approximately 80% in control non-cirrhotic livers. In rats made cirrhotic by bile-duct obstruction only, 10% efficiency of transduction was observed. Biodistribution analyses showed that vector expression was detected primarily in liver and at a low level in spleen and kidney. Although there was an important increase in liver enzymes between the first 48 h after adenovirus injection in cirrhotic animals compared to non-transduced cirrhotic rats, this hepatic damage was resolved after 72-96 h. Then, the cDNA for neutrophil collagenase, also known as Matrix Metalloproteinase 8 (MMP8), was cloned in an Ad-vector and delivered to cirrhotic rat livers being able to reverse fibrosis in 44%. This study demonstrates the potential use of adenoviral vectors in safe transient gene therapy strategies for human liver cirrhosis.

DDR2 receptor promotes MMP-2-mediated proliferation and invasion by hepatic stellate cells

Type I collagen provokes activation of hepatic stellate cells during liver injury through mechanisms that have been unclear. Here, we tested the role of the discoidin domain tyrosine kinase receptor 2 (DDR2), which signals in response to type I collagen, in this pathway. DDR2 mRNA and protein are induced in stellate cells activated by primary culture or in vivo during liver injury. The receptor becomes tyrosine phosphorylated in response to either endogenous or exogenous type I collagen, whereas its expression is downregulated during cellular quiescence induced by growth on Matrigel. We developed stellate cell lines stably overexpressing either wild-type DDR2, a constitutively active chimeric DDR2 receptor (Fc-DDR2), a truncated receptor expressing the extracellular domain, or a kinase-dead DDR2 Cells overexpressing DDR2 showed enhanced proliferation and invasion through Matrigel, activities that were directly related to increased expression of active matrix metalloproteinase 2 (MMP-2). These data show that DDR2 is induced during stellate cell activation and implicate the phosphorylated receptor as a mediator of MMP-2 release and growth stimulation in response to type I collagen. Moreover, type I collagen-dependent upregulation of DDR2 expression establishes a positive feedback loop in activated stellate cells, leading to further proliferation and enhanced invasive activity.

Activation of hepatic stellate cells in liver tissue of patients with fulminant liver failure after treatment with bioartificial liver

We studied the explanted livers from 12 patients with fulminant hepatic failure who were treated with a bioartificial liver and subsequently underwent orthotopic liver transplantation and from 18 patients who underwent orthotopic liver transplantation without previous treatment. Ten normal livers were used as controls. In addition to morphologic evaluation, an immunohistochemical analysis was performed with the monoclonal antibodies for alpha-smooth muscle actin and proliferation marker Ki-67. The expression of these markers was graded semiquantitatively from 0 to 3+ in a blinded fashion. The zonal distribution of activated hepatic stellate cells was also evaluated. In all cases, the hepatic stellate cells were activated and expressed alpha-smooth muscle actin. In all patients with submassive or massive liver cell necrosis, the distribution of activated hepatic stellate cells was predominantly in zone 1 of the acinus (periportal area). In contrast, in cases with early nodular regeneration and no significant fibrosis, the activated hepatic stellate cells were distributed throughout the liver parenchyma, involving zones 2 and 3 of the acinus. Expression of the proliferation marker Ki-67 was graded 3+ in all patients treated with the bioartificial liver who had orthotopic liver transplantation and 2+ in patients who underwent orthotopic liver transplantation only.

The role of tumor necrosis factor-alpha in liver toxicity, inflammation, and fibrosis induced by carbon tetrachloride

Hepatic expression of the proinflammatory cytokine tumor necrosis factor-alpha (TNFalpha) occurs in many acute and chronic liver diseases, as well as following exposure to hepatotoxic chemicals, and is believed to help influence both the damage and repair processes that occur following these insults by regulating additional mediators. We examined the role of TNFalpha in transgenic mice deficient in TNF receptors (TNFR) utilizing carbon tetrachloride (CCl(4)) as a model hepatotoxic agent that allowed for the evaluation of necrosis, inflammation, and fibrosis. Hepatocyte damage, as evident by local areas of liver necrosis and elevated levels of serum transaminase, occurred to a similar degree in wild-type and TNFR-deficient knockout (KO) mice following acute exposure to CCl(4). In contrast, the inflammatory response, manifested as an inflammatory cell influx, as well as induction of chemokines and adhesion molecules that occurred in wild-type mice following treatment with CCl(4), was not as evident in TNFR-KO mice. This response was associated primarily with type-1 (TNFR1) rather than type-2 (TNFR2) receptor responses. Liver fibrosis resulting from chronic CCl(4) exposure was also markedly dependent upon TNFalpha as demonstrated by almost a complete histological absence of fibrosis in TNFR-deficient mice. This was further supported by marked reductions in procollagen and transforming growth factor beta synthesis in TNFR-deficient mice. Taken together, these results indicate that TNFalpha is responsible for regulating products that induce inflammation and fibrosis but not direct hepatocyte damage in CCl(4)-induced hepatotoxicity.

DDR2 receptor promotes MMP-2-mediated proliferation and invasion by hepatic stellate cells

Type I collagen provokes activation of hepatic stellate cells during liver injury through mechanisms that have been unclear. Here, we tested the role of the discoidin domain tyrosine kinase receptor 2 (DDR2), which signals in response to type I collagen, in this pathway. DDR2 mRNA and protein are induced in stellate cells activated by primary culture or in vivo during liver injury. The receptor becomes tyrosine phosphorylated in response to either endogenous or exogenous type I collagen, whereas its expression is downregulated during cellular quiescence induced by growth on Matrigel. We developed stellate cell lines stably overexpressing either wild-type DDR2, a constitutively active chimeric DDR2 receptor (Fc-DDR2), a truncated receptor expressing the extracellular domain, or a kinase-dead DDR2 Cells overexpressing DDR2 showed enhanced proliferation and invasion through Matrigel, activities that were directly related to increased expression of active matrix metalloproteinase 2 (MMP-2). These data show that DDR2 is induced during stellate cell activation and implicate the phosphorylated receptor as a mediator of MMP-2 release and growth stimulation in response to type I collagen. Moreover, type I collagen-dependent upregulation of DDR2 expression establishes a positive feedback loop in activated stellate cells, leading to further proliferation and enhanced invasive activity.

Effects of hypoxia, hyperoxia on the regulation of expression and activity of matrix metalloproteinase-2 in hepatic stellate cells

AIM

To study the effects of hypoxia, hyperoxia on the regulation of expression and activity of matrix metalloproteinase-2 (MMP-2) in hepatic stellate cells (HSC).

METHODS

The expressions of MMP-2, tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) and membrane type matrix metalloproteinase-1 (MT1-MMP) in cultured rat HSC were detected by immunocytochemistry (ICC) and in situ hybridization (ISH). The contents of MMP-2 and TIMP-2 in culture supernatant were detected with ELISA and the activity of MMP-2 in supernatant was revealed by zymography.

RESULTS

In the situation of hypoxia for 12h, the expression of MMP-2 protein was enhanced (hypoxia group positive indexes: 5.7 +/- 2.0, n=10; control: 3.2 +/- 1.0, n = 7; P<0.05), while TIMP-2 protein was decreased in HSC (hypoxia group positive indexes: 2.5 +/- 0.7, n = 10; control: 3.6 +/- 1.0, n = 7; P < 0.05), and the activity (total A) of MMP-2 in supernatant declined obviously (hypoxia group: 7.334 +/- 1.922, n = 9; control: 17.277 +/- 7.424, n = 11; P < 0.01). Compared the varied duration of hypoxia, the changes of expressions including mRNA and protein level as well as activity of MMP-2 were most notable in 6h group. The highest value(A(hypoxia)-A(control)) of the protein and the most intense signal of mRNA were in the period of hypoxia for 6h, along with the lowest activity of MMP-2. In the situation of hyperoxia for 12h, the contents (A(450)) of MMP-2 and TIMP-2 in supernatant were both higher than those in the control, especially the TIMP-2 (hyperoxia group: 0.0499 +/- 0.0144, n = 16; control: 0.0219 +/- 0.0098, n = 14; P < 0.01), and so was the activity of MMP-2 (hyperoxia group: 5.252 +/- 0.771, n = 14; control: 4.304 +/- 1.083, n = 12; P < 0.05), and the expression of MT1-MMP was increased.

CONCLUSION

HSC is sensitive to the oxygen, hypoxia enhances the expression of MMP-2 and the effect is more marked at the early stage; hyperoxia mainly raises the activity of MMP-2.

Use of cultured cells in assessing ethanol toxicity and ethanol-related metabolism

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Terrence M. Donohue, Jr, and Dahn L. Clemens. The presentations were (1) Characterization of single and double recombinant hepatoma cells that express ethanol-metabolizing enzymes, by Terrence M. Donohue, Jr; (2) Inhibition of cell growth by ethanol metabolism, by Dahn L. Clemens; (3) Use of transfected HeLa cells to study the genesis of alcoholic fatty liver, by Andrea Galli and David Crabb; (4) CYP2E1-mediated oxidative stress induces COL1A2 mRNA in hepatic stellate cells and in a coculture system of HepG2 and stellate cells, by Natalia Nieto; (5) Transforming growth factor-alpha secreted from ethanol-exposed hepatocytes contributes to development of alcoholic hepatic fibrosis, by Junji Kato; and (6) Effect of ethanol on Fas-dependent caspase-3 activation and apoptosis in CD4+ T cells, by Shirish S. Barve.

Antifibrotic effect of silymarin in rat secondary biliary fibrosis is mediated by downregulation of procollagen alpha1(I) and TIMP-1

BACKGROUND/AIMS

Silymarin reduces hepatic collagen accumulation by 35% in rats with secondary biliary cirrhosis. The aim of the present study was to explore its antifibrotic mechanism.

METHODS

Thirty female adult Wistar rats were allocated to (1) bile duct occlusion, (2) bile duct occlusion and oral silymarin at 50 mg/kg per day, and (3) sham operation and oral silymarin at 50 mg/kg per day. Steady-state mRNA levels for procollagen alpha1(I), tissue inhibitor of metalloproteinases-1 (TIMP-1), and transforming growth factor (TGF) beta1 were determined by multi-probe ribonuclease protection assay.

RESULTS

After 6 weeks of bile duct occlusion, liver collagen content was increased 12-fold, when compared with the sham-operated controls. These animals displayed 17-, 6.5- and 16-fold higher transcript levels for procollagen alpha1(I), TIMP-1 and TGFbeta1 (P < 0.01). Silymarin downregulated elevated procollagen alpha1(I), TIMP-1 and TGFbeta1 mRNA levels by 40-60% (P < 0.01). These lowered hepatic profibrogenic transcript levels correlated with decreased serum levels of the aminoterminal propeptide of procollagen type III.

CONCLUSIONS

Silymarin suppresses expression of profibrogenic procollagen alpha1(I) and TIMP-1 most likely via downregulation of TGFbeta1 mRNA in rats with biliary fibrosis. The serum procollagen type III propeptide level mirrors profibrogenic mRNA expression in the liver.

Hemodynamic effects of Salvia miltiorrhiza on cirrhotic rats

Salvia miltiorrhiza (Sm) administration has been shown to reduce hepatic fibrosis in rats. We investigated the hemodynamic effects of Sm on bile duct ligated (BDL) rats. Hemodynamic, histological, and vascular contractile studies were conducted in rats 4 weeks after bile duct ligation. An aqueous extract of Sm (0.2 g twice per day) or vehicle was administered for 4 weeks to BDL rats. Sm treatment in BDL rats significantly reduced histological grades of fibrosis and ameliorated the portal hypertensive state (including portal venous pressure, superior mesenteric artery blood flow, cardiac index, and total peripheral resistance) as compared with vehicle treatment. Moreover, Sm treatment enhanced the vascular sensitivity of mesenteric arteries to phenylephrine in BDL rats. Sm treatment had no effect on plasma biochemical profiles of either BDL or normal rats. Our results suggest that 4-week Sm treatment ameliorates the portal hypertensive state in BDL rats.Key words: hemodynamics, fibrosis, portal hypertension, vascular contractile response, Salvia miltiorrhiza.

Inhibiting effect of antisense oligonucleotides phosphorthioate on gene expression of TIMP-1 in rat liver fibrosis

AIM

To observe the inhibition of antisense oligonucleotides (asON) phosphorthioate to the tissue inhibitors metalloproteinase-1 (TIMP-1) gene and protein expression in the liver tissue of immunologically induced hepatic fibrosis rats. The possibility of reversing hepatic fibrosis through gene therapy was observed.

METHODS

Human serum albumin (HSA) was used to attack rats, as hepatic fibrosis model, in which asONs were used to block the gene and protein expressing TIMP-1. According to the analysis of modulator, structure protein, coding series of TIMP-1 genome, we designed four different asONs. These asONs were injected into the hepatic fibrosis models through coccygeal vein. The results was observed by RT-PCR for measuring TIMP-1 mRNA expression, immunohistochemistry and in situ hybridization for collagen I, II, special staining of collagen fiber, and electron microscopic examination.

RESULTS

Hepatic fibrosis could last within 363 days in our modified model. The expressing level of TIMP-1 was high during hepatic fibrosis process. It has been proved by the immunohistochemical and the electron microscopic examination that the asON phosphorthioate of TIMP-1 could exactly express in vivo. The effect of colchicine was demonstrated to inhibit the expressing level of mRNA and the content of collagen I, III in the liver of experimental hepatic fibrosis rats. However, the electron microscopy research and the pathologic grading of hepatic fibrosis showed that there was no significant difference between the treatment group and the model group (P> 0.05).

CONCLUSION

The experimental rat model of hepatic fibrosis is one of the preferable models to estimate the curative effect of anti-hepatic fibrosis drugs. The asON phosphorthioate of TIMP-1 could block the gene and protein expression of TIMP-1 in the liver of experimental hepatic fibrosis rats at the mRNA level. It is possible to reverse hepatic fibrosis, and it is expected to study a new drug of antihepatic fibrosis on the genetic level. Colchicine has very limited therapeutic effect on hepatic fibrosis, furthermore, its toxicity and side effects are obvious.

Resolution of cirrhosis in autoimmune hepatitis with corticosteroid therapy

Successful therapy for liver diseases, including autoimmune hepatitis, primary biliary cirrhosis, and hepatitis C, has been associated with a reduction in hepatic fibrosis. Recently, a study of needle liver biopsy specimens documented resolution of cirrhosis in a small group of patients with autoimmune hepatitis who responded to corticosteroid therapy. We describe a woman with autoimmune hepatitis who had cirrhosis on a wedge biopsy of the liver in 1985 and who attained a biochemical response with immunosuppressive therapy. A repeat wedge liver biopsy performed 14 years later was normal, providing unequivocal evidence that cirrhosis can reverse completely in autoimmune hepatitis.

Use of cultured cells in assessing ethanol toxicity and ethanol-related metabolism

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Terrence M. Donohue, Jr, and Dahn L. Clemens. The presentations were (1) Characterization of single and double recombinant hepatoma cells that express ethanol-metabolizing enzymes, by Terrence M. Donohue, Jr; (2) Inhibition of cell growth by ethanol metabolism, by Dahn L. Clemens; (3) Use of transfected HeLa cells to study the genesis of alcoholic fatty liver, by Andrea Galli and David Crabb; (4) CYP2E1-mediated oxidative stress induces COL1A2 mRNA in hepatic stellate cells and in a coculture system of HepG2 and stellate cells, by Natalia Nieto; (5) Transforming growth factor-alpha secreted from ethanol-exposed hepatocytes contributes to development of alcoholic hepatic fibrosis, by Junji Kato; and (6) Effect of ethanol on Fas-dependent caspase-3 activation and apoptosis in CD4+ T cells, by Shirish S. Barve.

Proliferating bile duct epithelial cells are a major source of connective tissue growth factor in rat biliary fibrosis

Connective tissue growth factor (CTGF) is a downstream mediator of transforming growth factor-beta1 (TGF-beta1) and thus a potential target for antifibrotic treatment strategies. CTGF is up-regulated in disorders such as atherosclerosis, scleroderma, and fibrosis of kidneys and lungs. We investigated the temporospatial expression patterns of CTGF and TGF-beta1 mRNA in rat livers with acute fibrogenesis (after a single dose of CCl(4)) and with advanced fibrosis (6 weeks after complete bile duct occlusion). Multiprobe ribonuclease protection assay revealed increasing TGF-beta1 and CTGF mRNA levels 6 hours after injection of CCl(4), with peak levels after 72 hours. In biliary fibrosis TGF-beta1 and CTGF mRNA levels increased fourfold and sevenfold, respectively (P: < 0.001). In situ hybridization combined with cell-specific markers revealed CTGF transcripts in desmin-positive cells after a single dose of carbon tetrachloride, whereas no transcripts were found in normal livers. In biliary fibrosis, however, proliferating bile duct epithelial cells were the predominant source of CTGF mRNA. We conclude that in rat liver fibrogenesis CTGF is up-regulated in close association with TGF-beta1 and that, contrary to a previous report, not solely hepatic stellate cells but activated bile duct epithelial cells are the main source of this profibrogenic factor.