Inhibition of rat hepatic lipocyte activation in culture by interferon-gamma

Herbal medicine Sho-saiko-to (TJ-9) prevents liver fibrosis and enzyme-altered lesions in rat liver cirrhosis induced by a choline-deficient L-amino acid-defined diet

BACKGROUND/AIM

A herbal medicine, Sho-saiko-to (TJ-9), has recently been orally administered to patients with chronic liver disease in Japan and has been reported to inhibit the development of hepatocellular carcinoma. The aim of this study was to investigate whether TJ-9 has an inhibitory effect on the development of preneoplastic lesions and liver fibrosis in rats.

METHODS

The effects of the TJ-9 were examined using the choline-deficient L-amino acid-defined (CDAA) diet-induced liver fibrosis model in 16-week-old male Wistar rats.

RESULTS

TJ-9 (1% w/w) prevented fibrosis, as indicated by reduced hydroxyproline content in the liver and inhibition of the increase in a serum marker of fibrosis (hyaluronic acid), without reducing the increase in serum alanine aminotransferase and aspartate aminotransferase. TJ-9 also reduced the expression of type III procollagen alpha 1 mRNA in the liver, as well as the proliferation of myofibroblast-like cells (activated stellate cells, activated Ito cells). Furthermore, TJ-9 reduced the number of preneoplastic lesions, detected as enzyme-altered (glutathione S-transferase placental form-positive) lesions, in the liver.

CONCLUSIONS

These results indicate that the herbal medicine Sho-saiko-to (TJ-9) prevents fibrosis as well as preneoplastic lesions, not by inhibiting hepatocyte cell death but by inhibiting the activation of stellate cells, which are considered to be the main collagen-producing cells, leading to a reduction in the development of preneoplastic lesions.

Signal transduction in hepatic stellate cells

Hepatic stellate cells (HSC) are presently regarded as one of the key cell types involved in the progression of liver fibrosis and in the related pathophysiological and clinical complications. Following acute or chronic liver tissue damage, HSC undergo a process of activation towards a phenotype characterised by increased proliferation, motility, contractility and synthesis of extracellular matrix (ECM) components. Several factors have been shown to play a key role in the promotion of the full-blown picture of activated HSC. These include extensive changes in the composition and organisation of the ECM, the secretion of several growth factors, cytokines, chemokines, products of oxidative stress and other soluble factors. It is evident that each cellular response to extracellular stimuli must be framed in a scenario where different forces modulate one another and result in a prevalent biological effect. Along these lines, the identification and characterisation of intracellular signalling pathways activated by different stimuli in HSC represent a mandatory step. In this review article we have made an attempt to summarise recent acquisitions to our knowledge of the involvement of different intracellular signalling pathways in key aspects of HSC biology.

Effect of tumour necrosis factor-alpha on proliferation, activation and protein synthesis of rat hepatic stellate cells

BACKGROUND/AIMS

Hepatic stellate cells represent the principal matrix-synthesising cells of damaged liver and are targets of a number of cytokines currently under investigation. The study analyses the effects of tumour necrosis factor-alpha and interferon-gamma on proliferation, "activation" and protein synthesis of hepatic stellate cells.

METHODS

Primary cultures of hepatic stellate cells were exposed to tumour necrosis factor-alpha and interferon-gamma. Cell proliferation was studied by 3H-thymidine and bromo-deoxy-uridine incorporation. Protein synthesis was analysed using immunoprecipitation, Western- and Northern blotting techniques.

RESULTS

Proliferation of hepatic stellate cells was reduced by tumor necrosis factor-alpha and interferon-gamma, while "activation" of hepatic stellate cells as assessed by expression of smooth muscle alpha-actin and of TGF-beta/activin type I receptor was induced by tumour necrosis factor-alpha but downregulated by interferon-gamma. Tumour necrosis factor-alpha increased the synthesis of distinct extracellular matrix proteins, particularly of fibronectin and tenascin, but decreased collagen type III expression. In contrast, interferon-gamma reduced the synthesis of all connective tissue proteins tested. Among the protease inhibitors, interferon-gamma induced C1-esterase inhibitor synthesis, while tumour necrosis factor-alpha stimulated plasminogen activator inhibitor type 1 production.

CONCLUSIONS

Tumour necrosis factor-alpha and interferon-gamma decrease proliferation of hepatic stellate cells, while "activation" of hepatic stellate cells and synthesis of proteins involved in matrix metabolism are regulated in a differential, cytokine-specific manner, suggesting that both cytokines play an important role in liver repair.

gamma-Interferon inhibits secretin-induced choleresis and cholangiocyte proliferation in a murine model of cirrhosis

BACKGROUND/AIMS

Cholangiocyte proliferation is associated with increased secretin receptor gene expression and secretin-induced choleresis. Since gamma-interferon has antiproliferative effects, we tested the hypothesis that gamma-interferon inhibits ductal proliferation and secretin-stimulated choleresis associated with cirrhosis.

METHODS

Mice were treated with 0.1 ml of 25% carbon tetrachloride intraperitoneally twice weekly and 5% alcohol in drinking water for 12 weeks to induce cirrhosis and subsequently gamma-interferon 10(5) intramuscularly was administered daily for 10 weeks. We measured the effects of carbon tetrachloride and gamma-interferon on liver collagen content by morphometric analysis and hydroxyproline content. We measured the effects of gamma-interferon on ductal mass by morphometry and on ductal secretion by assessment of secretin receptor gene expression and secretin-induced choleresis.

RESULTS

Compared to controls, there was an increase in liver hydroxyproline content of carbon tetrachloride-treated mice with histologic evidence of cirrhosis. Gamma-interferon treatment significantly decreased collagen liver content with loss of histologic features of cirrhosis. Morphometry revealed an increased number of bile ducts in cirrhotic mice as compared to controls or cirrhotics who received gamma-interferon. Secretin receptor mRNA levels were higher in cirrhotic mice compared to controls but this increase was inhibited by gamma-interferon. Secretin stimulated ductal secretion in cirrhotic mice but not control or cirrhotic mice who received gamma-interferon.

CONCLUSIONS

We have established a murine model for cirrhosis and have shown, consistent with our hypothesis, that gamma-interferon decreases collagen content, ductal mass and secretin-induced choleresis incirrhotic mice.

Prolyl 4-hydroxylase inhibitor (HOE 077) inhibits pig serum-induced rat liver fibrosis by preventing stellate cell activation

BACKGROUND/AIMS

The aim of this study was to investigate the effect and mechanism of fibrosuppression by a newly synthesized prolyl 4-hydroxylase inhibitor [HOE 077, 2, 4-pyridine dicarboxylic acid bis [(2-methoxyethyl) amide]] on pig serum-induced liver fibrosis in the rat.

METHODS

Male Wistar rats received 0.5 ml of pig serum twice a week for 10 weeks with 0, 100 or 200 ppm of HOE 077. At the end of the experiment, the hydroxyproline content of the liver, and alanine aminotransferase were measured. Histological stains used were HE, azan and a stain for alpha-smooth muscle actin (alpha-SMA). Electron microscopy was also performed. Messenger RNA expressions of type I and III procollagen were examined by Northern blot analysis. alpha-SMA positive cells and fibers with azan staining were assessed as percent area of the tissue specimen, using an image analysis system.

RESULTS

Rats that received pig serum for 10 weeks showed an increased liver hydroxyproline content of 318+/-39 microg/g wet weight (n=15). HOE 077 at doses up to 200 ppm significantly (p<0.01) reduced this increase of liver hydroxyproline content (181+/-39 microg/g wet weight, n=15) in accordance with improved histological findings. 200 ppm of HOE 077 significantly reduced mRNA expressions of alpha2(I) (486+/-102 vs 151+/-36, p<0.01) and alpha1(III) (276+/-127 vs 160+/-67, p<0.05) procollagen and percent area of alpha-SMA positive cells (2.94+/-2.14 vs 1.17+/-0.88%). Electron microscopy revealed that 200 ppm of HOE 077 prevented the loss of fat droplets.

CONCLUSIONS

A prolyl 4-hydroxylase inhibitor (HOE 077) prevented pig serum-induced rat liver fibrosis by inhibiting stellate cell activation.

Lobular--but not periovular--inhibition of collagen deposition in the liver of S. mansoni infected mice using interferon-gamma

BACKGROUND/AIMS

Interferon-gamma (IFNgamma) elicits antiproliferative and antifibrogenic activity in a variety of mesenchymal cells, including hepatic stellate cells (Ito cells), and therefore represents a possible drug for liver fibrosis. However, IFNgamma binds to heparan sulfate, and is localized by these molecules in a restricted area within the tissue. For example, in rat liver, it has been shown that following injection, IFNgamma was concentrated in a restricted area by heparan sulfate. The aim of this study was to analyze, at the tissular level in the liver, the antifibrogenic activity of IFNgamma.

METHODS

Chronic inflammation due to Schistosoma infection induces hepatic fibrogenesis around the parasite eggs (portal fibrosis) and in the parenchyma (lobular fibrosis). Infected mice were treated with recombinant IFNgamma, and the collagen content of the liver was evaluated by means of biochemical dosages, histologic and morphometric examination of liver tissue, and electron microscopic analysis.

RESULTS

IFNgamma reduced the whole liver collagen content by 28% compared to control mice. In control mice, collagen was found around eggs and infiltrating the parenchyma, associated with a diffuse array of inflammatory cells, while in treated mice the collagen was present only around eggs and surrounded by a dense layer of inflammatory cells. Therefore, collagen was measured in isolated granulomas and in the remaining parenchyma. We found that IFNgamma strongly reduced the parenchymal collagen (74%), but had no effect on the granuloma collagen content.

CONCLUSIONS

Together these data demonstrate that IFNgamma did not act in a homogeneous manner in the liver. Since granulomas are almost completely devoid of heparan sulfate, these data could suggest, among others hypotheses, that heparan sulfate which binds IFNgamma either localizes or mediates the cytokine activity outside the granulomas.

The hepatic stellate (Ito) cell: its role in human liver disease

The hepatic stellate (Ito) cell lies within the space of Disse and has a variety of functions. Stellate cells store vitamin A in characteristic lipid droplets. In the normal human liver, the cells can be identified by the presence of these lipid droplets; in addition, many stellate cells in the normal liver express alpha-smooth muscle actin. In acute liver injury, there is an expansion of the stellate cell population with increased alpha-smooth muscle actin expression; stellate cells appear to play a role in extracellular matrix remodelling after recovery from injury. In chronic liver injury, the stellate cell differentiates into a myofibroblast-like cell with marked expression of alpha-smooth muscle actin and occasional expression of desmin. Myofibroblast-like cells have a high fibrogenic capacity in the chronically diseased liver and are also involved in matrix degradation. In vitamin A intoxication, hypertrophy and proliferation of the stellate and myofibroblast-like cells may lead to non-cirrhotic portal hypertension, fibrosis and cirrhosis. In liver tumours, myofibroblast-like cells are involved in the capsule formation around the tumour and in the production of extracellular matrix within it. The transition of stellate cells into myofibroblast-like cells is regulated by an intricate network of intercellular communication between stellate cells and activated Kupffer cells, damaged hepatocytes, platelets, endothelial and inflammatory cells, involving cytokines and nonpeptide mediators such as reactive oxygen species, eicosanoids and acetaldehyde. The findings suggest that the stellate cell plays an active role in a number of human liver diseases, with a particular reactivity pattern in fibrotic liver disorders.

Interferon-gamma-mediated activation of STAT1alpha regulates growth factor-induced mitogenesis

Immunomodulatory cytokines and growth factors act in a complex network to regulate diverse biologic processes. Pre-treatment of two types of human vascular pericytes, liver fat-storing cells or glomerular mesangial cells, with IFN-gamma dramatically enhanced DNA synthesis in response to PDGF or EGF. IFN-gamma by itself had very little effect on DNA synthesis. At least 24-h exposure of the cells to IFN-gamma is required for enhancement of growth factor-induced mitogenesis. IFN-gamma pretreatment did not influence PDGF or EGF receptor autophosphorylation, activation of phospholipase Cgamma1, and phosphatidylinositol 3-kinase, or mitogen-activated protein kinase activity. However, IFN-gamma pretreatment markedly potentiated the DNA binding activity of STAT1alpha in response to PDGF or EGF. Incubation of cells with antisense oligonucleotides targeting STATlalpha mRNA resulted in inhibition of DNA synthesis induced by the combination of IFN-gamma and PDGF or EGF. These data indicate that interaction between IFN-gamma and growth factors at the level of STAT1alpha results in increased DNA synthesis, and establish a role for STAT1alpha in this important biologic function of growth factors.

Alpha-interferon prevents liver collagen deposition and damage induced by prolonged bile duct obstruction in the rat

BACKGROUND/AIMS

Interferons have been used to treat chronic viral hepatitis, due to their antiviral properties. However, interferons are now recognized also to inhibit collagen production. Since fibrosis has been associated with liver damage and dysfunction, the effects of interferon-alpha 2 b on biliary obstruction-induced fibrosis were investigated.

METHODS

Extrahepatic cholestasis was induced in male Wistar rats (around 200g) by double ligation and division of the common bile duct. Control rats were sham operated. Interferon-alpha 2b (IFN-alpha; 100,000 IU/rat) was administered subcutaneously, daily after surgery. The animals were killed after 4 weeks of bile duct ligation or sham operation. Liver damage and cholestasis was analyzed by histological, ultrastructural and biochemical techniques.

RESULTS

Biliary obstruction produced dilation of the bile canaliculi, disorganization of mitochondria and an increase in vacuolization. Bile duct ligation led to an important accumulation of collagen, determined, both histologically and as the hydroxyproline content of the liver. Bilirubin and serum enzyme activities (determined as markers of cholestasis) increased several-fold after bile duct ligation. Administration of IFN-alpha to bile duct ligated rats resulted in significant preservation of ultrastructure, histology, inhibition of collagen accumulation and in a partial improvement of serum markers of cholestasis.

CONCLUSIONS

It is concluded that interferons possess interesting beneficial effects on the liver not related to its antiviral properties but probably associated with its antifibrogenic properties.

Inhibition of myofibroblastic transformation of cultured rat hepatic stellate cells by methylxanthines and dibutyryl cAMP

Stellate cells isolated from rat liver and cultured on uncoated plastic plates in serum-containing medium started proliferating and transforming to myofibroblastic cells. However, stellate cells did not proliferate when cultured in the presence of 3-isobutyl-1-methylxanthine or dibutyryl cAMP (dBcAMP). These substances significantly reduced [3h] thymidine incorporation of the proliferating cells. Morphologically, stellate cells cultured in the presence of 3-isobutyl-1-methylxanthine or dibutyryl cAMP kept well-developed processes and lipid droplets while untreated cells exhibited myofibroblastic characteristics. Western blot analysis and immunocytochemical studies revealed that 3-isobutyl-1-methylxanthine and dBcAMP suppressed the expression of alpha-smooth muscle actin in stellate cells. 3-isobutyl-1-methylxanthine increased the cellular levels of cAMP from a basal value of 0.7 +/- 0.1 to 8.5 +/- 1.7 pmol/well in stellate cells. Thus, 3-isobutyl-1-methylxanthine and dBcAMP inhibit the myofibroblastic transformation of stellate cells in vitro in some cAMP-related mechanism.

Liver stellate cells in chronic viral hepatitis: the effect of interferon therapy

BACKGROUND/AIMS

Liver stellate cell proliferation and differentiation into myofibroblast-like cells is related to the development of liver fibrosis. Several cytokines, including interferons, regulate liver stellate cell proliferation and phenotypic modulation. Recent studies indicate that human liver stellate cells express the alpha-isotype of actin, specific to smooth muscle cell differentiation. We aimed to evaluate the expression of alpha-smooth muscle actin-positive liver stellate cells in patients with chronic viral hepatitis and to evaluate whether and how such expression can be modified by alpha-interferon treatment.

METHODS

Using immunohistochemistry, and a semi-quantitative scoring method, we evaluated alpha-smooth muscle actin expression in liver stellate cells before and after alpha-interferon therapy in a series of liver biopsies from 44 patients with chronic viral hepatitis.

RESULTS

Before therapy, a large number of liver stellate cells expressing alpha-smooth muscle actin were present throughout all acinar zones. A significant reduction in alpha-smooth muscle actin expression by liver stellate cells was demonstrated in biopsies performed after suspending the interferon treatment. The drop in the number of alpha-smooth muscle actin-labelled cells after therapy correlated closely with the improvement in the histological index of activity.

CONCLUSIONS

The results suggest a specific effect of interferon on liver stellate cells, possibly related to its anti-inflammatory action.

Action of endothelins on hepatic stellate cells

To elucidate the role played by hepatic sinusoidal cells in the regulation of the circulatory status in the liver, the effect of endothelins (ETs) on primary-cultured stellate cells was examined. Kinetic analysis with 125I-labeled ET-1 revealed that stellate cells have ET receptors with a Kd value of 141 pM and a Bmax of 12.3 fmol/10(5) cells. ET-1, -2, and -3 dose-dependently increased inositol monophosphate (InsP) levels in stellate cells with an EC50 of 0.53, 1.63, and 1.88nM, respectively. Binding of 125I-labeled ET-1 to stellate cells and the ET-enhanced InsP formation were suppressed by preincubating the cells with 10 nM of unlabeled ET-1 or ET-3 for more than 3 h, indicating down-regulation and desensitization of ET receptors by homologous ligands. Binding of ETs to surface receptors induced a marked contraction of stellate cells. Stellate cells rapidly reacted to ETs, as detected by the flexible silicone-rubber-membrane method; 78%, 73%, and 58% of the stellate cells contracted 2.5 min after the addition of 10 nM of ET-1, ET-2, or ET-3, respectively. On the other hand, ETs also triggered a long-lasting contraction of the cells, as revealed with hydrated collagen gels. The ET-induced contraction of stellate cells decreased the diameter of the collagen lattice by about 60%, and this action was inhibited either by cytochalasin B or by H-7, a protein kinase C inhibitor. These and other results suggest that ETs induced cell contraction by some mechanism that involved protein kinase C.

New prolyl 4-hydroxylase inhibitor reduces procollagen gene expression and enzyme-altered lesions in rat liver cirrhosis

A choline deficient L-amino acid defined (CDAA) diet led to the development of liver cirrhosis in male Wistar rats after 16 weeks. A new prolyl 4-hydroxylase inhibitor, 2,4-pyridine dicarboxylic acid bis [(2-methoxyethyl amide)] (HOE 077), prevented liver fibrosis in a dose-dependent manner without a reduction in increased serum alanine aminotransferase and aspartate aminotransferase in parallel with a reduction in preneoplastic enzyme-altered lesions stained with anti-glutathione S-transferase placental form antibody. HOE 077 reduced the increase in serum procollagen III peptide (PIIIP) in a dose-dependent manner and in proportion to the reduction in mRNA expression of type III procollagen in the liver of rats fed a CDAA diet.

Remission of liver fibrosis by interferon-alpha 2b

Fibrosis is a dynamic process associated with the continuous deposition and resorption of connective tissue, mainly collagen. Therapeutic strategies are emerging by which this dynamic process can be modulated. Since interferons are known to inhibit collagen production, the aim of this study was to investigate if the administration of interferon-alpha 2b (IFN-alpha) can restore the normal hepatic content of collagen in rats with established fibrosis. Fibrosis was induced by prolonged bile duct ligation. IFN-alpha (100,000 IU/rat/day; s.c.) was administered to fibrotic rats for 15 days. Bile duct ligation increased liver collagen content 6-fold. In addition, serum and liver markers of hepatic injury increased significantly; liver histology showed an increase in collagen deposition, and the normal architecture was lost, with large zones of necrosis being observed frequently. IFN-alpha administration reversed to normal the values of all the biochemical markers measured and restored the normal architecture of the liver. Our results demonstrated that IFN-alpha is useful in reversing fibrosis and liver damage induced by biliary obstruction in the rat. However, further investigations are required to evaluate the therapeutic relevance of interferons on non-viral fibrosis and cholestasis.

Interferon alfa and gamma inhibit proliferation and collagen synthesis of human Ito cells in culture

During the course of ongoing liver fibrogenesis, Ito cells acquire myofibroblastic features, proliferate, and synthesize increased amounts of extracellular matrix components. Interferon (IFN) alfa and IFN gamma have been shown to elicit antiproliferative and/or antifibrogenic effects in various cell cultures of mesenchymal origin. The aim of this study was to investigate the effects of IFN-alpha and IFN-gamma on cultured human myofibroblastic Ito cells (MFBIC) proliferation and collagen synthesis and secretion. Serum-stimulated incorporation of [3H]-thymidine into DNA of MFBIC was dose-dependently decreased by both cytokines. IFN-alpha (10(4) U/mL) and IFN-gamma (10(3) U/mL) decreased DNA synthesis by 69% and 66%, respectively. Inhibition of cell proliferation was confirmed by cell counting. Similar results were observed when cell growth was stimulated with platelet-derived growth factor (PDGF-BB, PDGF-AA) or transforming growth factor (TGF)-beta 1. Collagen secretion per cell was inhibited by both cytokines, as assessed by [3H]-hydroxyproline incorporation. After a 6-day treatment, IFN-gamma showed a greater potency than IFN-alpha in inhibiting secretion of newly synthetized collagen (41% and 4% of control in the presence of 10(2) U/mL of IFN-gamma and 10(4) U/mL of IFN-alpha, respectively). Both IFN-alpha and IFN-gamma concurrently decreased steady-state expression of type I and type III procollagen messenger RNAs (mRNAs) in quiescent MFBIC. Viability assays ruled out cytotoxic effects of the two molecules. Finally, both IFNs decreased smooth muscle alpha-actin (SM alpha-actin) expression, whether assayed by immunoblotting or by Northern blot analysis. We conclude that IFN-alpha and IFN-gamma inhibit proliferation as well as collagen synthesis in human MFBIC.

Modulation of experimental mesangial proliferative nephritis by interferon-gamma

The observation that interferon-gamma (IFN-gamma) inhibits cell proliferation and collagen synthesis of a variety of cell types in culture has suggested that IFN-gamma may be useful in the treatment of fibroproliferative diseases. We administered recombinant IFN-gamma subcutaneously (10(5) U/kg/day for 3 days) to rats, beginning one day after the induction of mesangial proliferative nephritis with anti-Thy 1 antibody. IFN-gamma reduced glomerular (primarily mesangial) cell proliferation by 44% at days 2 and 4 compared to vehicle injected control rats with anti-Thy 1 nephritis (that is, proliferating cells that excluded the macrophage marker, ED-1, P < 0.001). Despite the inhibition of mesangial cell proliferation, IFN-gamma did not reduce the overall extracellular matrix deposition (by silver stain) or deposition of type IV collagen or laminin (by immunostaining) at 4 or 7 days, and glomerular type IV collagen and laminin mRNA levels were increased (1.4 and 1.7-fold) at 4 days relative to controls. The inability of IFN-gamma treatment to reduce mesangial matrix expansion may relate to the fact that IFN-gamma treated rats had a twofold increase in glomerular macrophages (that is, ED-1 positive cells, P < 0.001 at 2 and 4 days) with an increase in oxidant producing cells (day 2, P < 0.05) and a 1.6-fold increase in glomerular TGF-beta mRNA expression (4 days). This suggests that the effect of IFN-gamma to inhibit mesangial cell proliferation in glomerulonephritis may be offset by the ability of IFN-gamma to increase glomerular macrophages and TGF-beta expression. These data also show that IFN-gamma can partly dissociate the mesangial proliferative response from the extracellular matrix expansion in glomerulonephritis.

Activation of Ito cells involves regulation of AP-1 binding proteins and induction of type I collagen gene expression

Activation of liver Ito cells is characterized by increased proliferation, fibrogenesis, loss of cellular retinoid and change of cell-shape. Here, we have described fundamental differences between freshly isolated Ito cells (FIC) and long-term cultured Ito cells (LTIC). This process of activation correlates with the absence of expression of Pro alpha 1(I) gene in FIC. LTIC expressed abundant transcripts of Pro alpha 1(I) gene. Nuclear run-off experiments showed the inability of FIC to support Pro alpha 1(I) RNA transcription while LTIC transcribed it greater than 5-fold as compared with FIC. Transforming growth factor beta (TGF beta)-treated LTIC had a preferential increase in the rate of Pro alpha 1(I) gene transcription as compared with control LTIC. A human collagen type I promoter-enhancer construct (pCOL-KT) [Thompson, Simkevich, Holness, Kang and Raghow (1991) J. Biol. Chem. 266, 2549-2556] was readily expressed in LTIC but failed to be expressed in FIC. Furthermore, TGF beta treatment of LTIC resulted in an increased expression of pCOL-KT. The deletion of an activator protein-1 (AP-1) binding site (+598 to +604) in the 360 bp enhancer region of pCOL-KT (S360) caused decreased expression of the CAT reporter gene, suggesting that this bonafide AP-1 site can, at least in part, mediate the transactivation effect of TGF beta. Using DNAase I protection, we demonstrate a single foot-print located at +590 to +625 in the S360 fragment; nuclear extracts prepared from TGF beta-treated LTIC exhibited greater activity of these AP-1 binding proteins. Gel mobility assays corroborated and extended the footprinting observation. No AP-1-binding activity was found in the nuclear extracts of FIC. Double-stranded oligonucleotides containing the consensus AP-1 motif were able to compete out the binding; consensus NF-1 motif oligonucleotides failed to do so. The preincubation of nuclear extracts from control and TGF beta-treated LTIC with antibodies against c-jun and c-fos rendered a reduced binding of AP-1 proteins to the target S360 fragment.

Inhibition of hepatic fibrogenesis: a review of pharmacologic candidates

Therapeutic attempts with anti-fibrotic drugs are still at an experimental stage. The clinical efficacies of most agents listed in Table II have not been proved. Some potential agents, such as colchicine, analogues of PGE, gamma-interferon, inhibitors of prolyl hydroxylase, malotilate, and PUL, must be further evaluated in controlled clinical trials. In addition, almost all anti-fibrotic agents, except HOE 077, are neither liver-nor fibrosis-specific. Some site-directed (targeted) drug delivery systems, drug-loaded vesicle carrier systems, like liposomes and erythrocyte ghosts, which selectively affect the extracellular matrix-producing cells, may improve efficacy and reduce adverse effects if they can be carriers for anti-fibrotic agents. Developments in biochemistry, immunohistochemistry, and molecular biology have considerably advanced our understanding of pathogenic mechanisms of hepatic fibrosis. With the development of available pathologic and serologic markers for ongoing fibrogenesis, experimental and clinical anti-fibrotic trials have become more active. Some therapeutic strategies have chosen targets for interference in collagen metabolism. In vivo inhibition of Ito cell activation has been a focus for the anti-fibrotic studies (70). In the present review an update of pharmacologic intervention in the process of metabolic pathways of collagen, the main extracellular matrices in both interstitium and basement membrane, has been summarized. Several drugs or biochemical agents that act on different steps of collagen synthesis, crosslinking, and breakdown are listed and discussed briefly. Moreover, agents that inhibit other matrix components are also involved in the review.(ABSTRACT TRUNCATED AT 250 WORDS)

An interleukin-1 receptor antagonist decreases fibrosis induced by dimethylnitrosamine in rat liver

The main pathological feature of liver fibrosis is the accumulation of extracellular matrix associated with hyperplasia and activation of perisinusoidal (Ito) cells (PSC) to myofibroblast-like cells. Interleukin-1 enhances collagen synthesis by increasing the proliferative activity of cultured PSC and has been implicated in the pathogenesis of hepatic fibrosis. Interleukin-1 receptor antagonist (IL-1ra) can block the binding of IL-1 to its receptors and act as a natural inhibitor of IL-1. We have examined whether the administration of IL-1ra can interfere with the development of experimental cirrhosis induced by dimethylnitrosamine (DMN). Rats were divided in three groups and received respectively DMN, DMN + IL-1ra and IL-1ra. For each group the collagen content of the hepatic tissue and the volume density of the inflammatory infiltrate were measured. Immunostaining for laminin and alpha-smooth muscle actin were also performed. In animals given DMN + IL-1ra we observed a decreased deposition of laminin and collagen, and a decreased number of laminin-positive PSC and of alpha-smooth muscle actin reactive cells, compared with animals receiving DMN alone. The present findings suggest that the early activation of PSC in vivo is at least in part mediated by IL-1 and confirm that the administration of IL-1ra may be of interest in modifying the biological effects of IL-1.

Activation-dependent contractility of rat hepatic lipocytes in culture and in vivo

Hepatic lipocytes are perisinusoidal cells that have been thought to be analogous to tissue pericytes, a cell type with purported vasoregulatory properties. However, we and others have recently demonstrated that lipocytes acquire markers of smooth muscle cells or myofibroblasts only after liver injury, via a process termed "activation." In this study, we document lipocyte contractility on collagen lattices and examine the importance of activation in this process. In culture, lipocytes became contractile only after spreading and activating, coincident with expression of smooth muscle alpha actin, a marker of activation (1990. Virchows Arch. B Cell Pathol. 59:349). After 5 d in culture, lipocytes induced rapid and sustained contraction of collagen lattices (to 43.7 +/- 2.3% of their original size 24 h after detachment). There was no contraction of lattices containing hepatocytes. Scanning electron microscopy demonstrated intimate associations of lipocyte cell membranes and collagen fibrils. Reduction in cell volume during contraction was also prominent. Lattice contraction by lipocytes was proportional to cell number. Serum was a potent stimulator of lipocyte contraction, as were endothelin types 1, 2, and 3; the effect of serum and endothelin 1 were additive. Neither thrombin, angiotensin-II, serotonin, nor the cytokines PDGF and TGF beta induced contraction. Cytochalasin B treatment resulted in concentration-dependent inhibition of contraction. As a test of the in vivo relevance of the culture findings, lipocytes were isolated from fibrotic animals and examined immediately after adherence. Whereas lipocytes from normal liver were initially compact, smooth muscle alpha actin negative and noncontractile, cells from animals with hepatic injury due to CCl4 displayed an activated appearance, expressed smooth muscle alpha actin, and were contractile immediately after adherence. Additionally, IFN-gamma, an agent which blocks lipocyte activation (1992. Hepatology. 16:776), inhibited lipocyte contraction. The data document that normal (i.e., quiescent) lipocytes are not contractile, but that activation is associated with the development of contractility. These findings suggest that a role for lipocytes in organ contraction or vasoregulation may be confined to injured, not normal liver.

New challenges in hepatic fibrosis

Treatment of hepatic fibrosis by simple and inexpensive therapies is a new challenge for the near future. Hepatic fibrosis which may lead to cirrhosis, is indeed associated with most chronic liver diseases and affects millions of people. During the last decade, major breakthroughs have been accomplished in the field of hepatic fibrosis including the discovery of key components of the extracellular matrix, the cellular origin of most matrix proteins, the molecular mechanisms involved in their synthesis and degradation, and the role of cytokines in fibrogenesis. Most of this progress came from the development of new techniques including in vitro model systems which have proven useful for investigating the molecular bases of fibrogenesis. From basic research to clinical application, two major fields are now actively explored: the search for reliable serum markers of fibrogenesis and the discovery of drugs that prevent cirrhosis. A recent approach to treat hepatic fibrosis is to use cytokines, e.g. interferons, that modulate extracellular matrix synthesis.