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

Therapeutic efficacy of Traditional Chinese Medicine 319 recipe on hepatic fibrosis induced by carbon tetrachloride in rats

BACKGROUND/AIMS

Hepatic fibrosis is a consequence of severe liver damage that occurs in many patients with chronic liver diseases. TCM 319 recipe is a Chinese Medicine formula which consists of six Chinese herbs. In this study, we investigated the anti-fibrotic efficacy and mechanisms of TCM 319 recipe.

METHODS

Hepatic fibrosis in rats was induced by carbon tetrachloride (CCl4). 34 male adult SD rats were allocated into five groups (group 1-concomitant CCl4 and TCM 319 recipe for 8 weeks; group 2-CCl4 for 4 weeks and then CCl4 and TCM 319 recipe for 4 weeks; group 3-CCl4 alone for 8 weeks; group 4-TCM 319 recipe only for 8 weeks; group 5-untreated controls). After 8 weeks of treatment, serum ALT assay, liver tissue histological examination and immunostaining were carried out to examine the liver function and fibrosis degree. The expression levels of platelet derived growth factor (PDGF-B), PDGF-Rbeta, and transforming growth factor-beta 1 (TGF-beta1) were measured by quantitative RT-PCR and western blot.

RESULTS

TCM 319 recipe reduced liver injury and attenuated hepatic fibrosis in group 1 compared with that in group 3. TCM 319 recipe suppressed the mRNA expression of tissue inhibitor of metalloproteinase 1 (TIMP-1). In addition, treatment with TCM 319 recipe significantly down-regulated mRNA expression of PDGF-B and PDGF-Rbeta, and it also suppressed protein expression of PDGF-Rbeta and TGF-beta1.

CONCLUSIONS

TCM 319 recipe extracts could attenuate hepatic fibrosis induced by CCl4 in rats. The anti-fibrotic effect of TCM 319 recipe is associated with the down-regulation of mRNA expression of TIMP-1, PDGF-B and PDGF-Rbeta, and with the suppression of protein expression of PDGF-Rbeta and TGF-beta1.

Effects of gadolinium-based magnetic resonance imaging contrast agents on human skin in organ culture and human skin fibroblasts

OBJECTIVE

Nephrogenic systemic fibrosis (NSF) is a clinical syndrome linked with exposure in renal failure patients to gadolinium-based magnetic resonance imaging contrast agents (GBCAs). The pathogenesis of the disease is largely unknown. The present study addresses potential pathophysiological mechanisms.

MATERIALS AND METHODS

Here, we have examined human skin in organ culture and human dermal fibroblasts in monolayer culture for responses to GBCA stimulation.

RESULTS

Treatment of normal human skin in organ culture with Omniscan had no significant effect on type I procollagen but increased both matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases-1. At the histologic level, many interstitial cells demonstrated cytologic features characteristic of activation (ie, light staining, oblong, plump nuclei). Omniscan, as well as 3 other magnetic resonance imaging contrast agents (Magnevist, Multihance, and Prohance), increased proliferation of human dermal fibroblasts in monolayer culture. Increased proliferation was accompanied by an increase in production of both matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases-1 but no increase in type I procollagen. Concentrations required for effects differed among the 4 agents (Omniscan < Magnevist and Multihance < Prohance). In contrast to its effects on fibroblast function, Omniscan did not stimulate human epidermal keratinocyte proliferation when examined over a wide range of concentrations.

CONCLUSION

These data provide evidence that GBCA exposure in ex vivo skin from healthy individuals increases fibroblast proliferation and has effects on the enzyme/inhibitor system that regulates collagen turnover in the skin.

Zinc supplementation attenuates ethanol- and acetaldehyde-induced liver stellate cell activation by inhibiting reactive oxygen species (ROS) production and by influencing intracellular signaling

BACKGROUND/AIMS

Zinc has been reported to prevent and reverse liver fibrosis in vivo; however, the mechanisms of its action are poorly understood. We therefore aimed to determine the antifibrotic potential of zinc.

METHODS

Assessed was the influence of preincubation of rat HSCs with 30 microM ZnCl2 on ethanol- (in the presence of 4-methyl pyrazole (4-MP)) or acetaldehyde-induced toxicity, apoptosis, migration, expression of smooth muscle alpha-actin (alpha-SMA) and procollagen I, release of reactive oxygen species (ROS), tumor necrosis factor-alpha (TNF-alpha), tumor growth factor-beta1 (TGF-beta1), metalloproteinase-2 (MMP-2) and tissue inhibitors of metalloproteinases (TIMPs) production. Intracellular signals such as nuclear factor-kappaB (NFkappaB), C-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) induced by ethanol and its metabolite were also assessed.

RESULTS

30 microM zinc protected HSCs against ethanol and acetaldehyde toxicity and inhibited their apoptosis. Zinc inhibited the production of ROS by HSCs treated with ethanol and acetaldehyde and inhibited their migration. Zinc also inhibited ethanol- and acetaldehyde-induced TGF-beta1 and TNF-alpha production. Zinc down-regulated ethanol- and acetaldehyde-induced production of TIMP-1 and TIMP-2 and decreased the activity of MMP-2. In ethanol- and acetaldehyde-induced HSCs, zinc inhibited the activation of the p38 MAPK as well as the JNK transduction pathways and phosphorylation of IkappaB and Smad 3.

CONCLUSION

The results indicated that zinc supplementation inhibited ethanol- and acetaldehyde-induced activation of HSCs on different levels, acting as an antioxidant and inhibitor of MAPK, TGF-beta and NFkappaB/IkappaB transduction signaling. The remarkable inhibition of several markers of HCS activation makes zinc a promising agent for antifibrotic combination therapies.

Protective effect of a mixture of Aloe vera and Silybum marianum against carbon tetrachloride-induced acute hepatotoxicity and liver fibrosis

The hepatoprotective effects of ACTIValoe N-931 complex, a mixture of Aloe vera and Silybum marianum, against acute and chronic carbon tetrachloride (CCl(4))-induced liver injuries were investigated. Acute hepatotoxicity was induced by intraperitoneal injection of CCl(4) (50 microl/kg), and ACTIValoe N-931 complex at 85, 170, and 340 mg/kg was administered orally 48, 24, and 2 h before and 6 h after injection of CCl(4). Hepatotoxicity was assessed 24 h after CCl(4) treatment. Liver fibrosis was induced by intraperitoneal injection of CCl(4) for 8 weeks (0.5 ml/kg, twice per week), and mice were treated with ACTIValoe N-931 complex at 85, 170, or 340 mg/kg once a day (p.o.). In both acute hepatotoxicity and liver fibrosis, serum aminotransferase levels and lipid peroxidation were increased and the hepatic glutathione content was decreased. These changes were prevented by ACTIValoe N-931 complex. The ACTIValoe N-931 complex attenuated the increase in tumor necrosis factor-alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), mRNA expressions in acute hepatotoxicity. In antifibrotic experiments, tissue inhibitor of metalloprotease-1 (TIMP-1) mRNA expression was attenuated by treatment with ACTIValoe N-931 complex. The ACTIValoe N-931 complex decreased the hepatic hydroxyproline content and the transforming growth factor-beta1 levels. Our results suggest that the ACTIValoe N-931 complex has hepatoprotective effects in both acute and chronic liver injuries induced by CCl(4).

The effects of N-acetylcysteine on the expression of matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase-2 in hepatic fibrosis in bile duct ligated rats

AIM

N-acetylcysteine can inhibit the formation of intracellular reactive oxygen intermediates. Cellular redox state plays a role in regulating the secretion of matrix metalloproteinase-2. We investigated the effects of N-acetylcysteine on the expression of matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase-2.

METHODS

Bile duct ligated rats were used as a model of hepatic fibrosis. We compared the level of gene expression (using real-time reverse transcription polymerase chain reaction [RT-PCR]), liver function parameters, hepatic reactive oxygen production, lipid peroxidation and glutathione state in experimental groups.

RESULTS

N-acetylcysteine treatment significantly improved liver function parameters including the plasma levels of aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase and bilirubin. In addition, significant improvement of glutathione state and reactive oxygen production were observed. Hepatic lipid peroxidation was reversed by N-acetylcysteine treatment. Although N-acetylcysteine treatment did not completely normalize the increased matrix metalloproteinase-2 expression, it significantly decreased its level by 65%. N-acetylcysteine treatment also significantly decreased matrix metalloproteinase-2 activity and normalized tissue inhibitor of matrix metalloproteinase-2 expression.

CONCLUSION

Collectively, N-acetylcysteine showed inhibition of matrix metalloproteinase-2 expression and activity. In addition, administration of N-acetylcysteine was associated with downregulation of the expression of tissue inhibitor of matrix metalloproteinase-2 and amelioration of oxidative stress in the liver of bile duct ligated rats.

Advances in antifibrotic therapy

Sustained progress in defining the molecular pathophysiology of hepatic fibrosis has led to a comprehensive framework for developing antifibrotic therapies. Indeed, the single greatest limitation in bringing new drugs to the clinical setting is a lack of clarity regarding clinical trial and treatment end points, not a lack of promising agents. A range of treatments, including those developed for other indications, as well as those specifically developed for hepatic fibrosis, are nearing or in clinical trials. Most are focused on attacking features of either hepatic injury and/or activated stellate cells and myofibroblasts, which are the primary sources of extracellular matrix (scar) proteins. Thus, features of injury and stellate cell activation provide a useful template for classifying these emerging agents and point to a new class of therapies for patients with fibrosing liver disease.

Fibrosis and cirrhosis reversibility - molecular mechanisms

The concept that liver fibrosis is a dynamic process with potential for regression as well as progression has emerged in parallel with clinical evidence for remodeling of fibrotic extracellular matrix in patients who can be effectively treated for their underlying cause of liver disease. This article reviews recent discoveries relating to the cellular and molecular mechanisms that regulate fibrosis regression, with emphasis on studies that have used experimental in vivo models of liver disease. Apoptosis of hepatic myofibroblasts is discussed. The functions played by transcription factors, receptor-ligand interactions, and cell-matrix interactions as regulators of the lifespan of hepatic myofibroblasts are considered, as are the therapeutic opportunities for modulating these functions. Growth factors, proteolytic enzymes, and their inhibitors are discussed in detail.

Hepatic fibrosis -- overview

The study of hepatic fibrosis, or scarring in response to chronic liver injury, has witnessed tremendous progress in the past two decades. Clarification of the cellular sources of scar, and emergence of hepatic stellate cells not only as a fibrogenic cell type, but also as a critical immunomodulatory and homeostatic regulator are among the most salient advances. Activation of hepatic stellate cells remains a central event in fibrosis, complemented by evidence of additional sources of matrix-producing cells including bone marrow, portal fibroblasts, and epithelial-mesenchymal transition from both hepatocytes and cholangiocytes. A growing range of cytokines and their receptors and inflammatory cell subsets have further expanded our knowledge about this dynamic process. Collectively, these findings have laid the foundation for continued elucidation of underlying mechanisms, and more importantly for the implementation of rationally based approaches to limit fibrosis, accelerate repair and enhance liver regeneration in patients with chronic liver disease.

Inhibition of inducible nitric oxide synthase activity prevents liver recovery in rat thioacetamide-induced fibrosis reversal

BACKGROUND

Stimulation of nitric oxide (NO) synthesis similar to the application of NO donors could be of benefit in liver fibrosis. Many authors believe that activation of NO synthesis by pharmacological agents is promising in the treatment of liver fibrosis. However, there is considerable controversy in understanding the role of NO in fibrogenesis and fibrolysis. The aims of our study were to evaluate the effects of L-arginine, as an NO metabolic precursor, and those of NO synthase (NOS) inhibitors, L-nitroarginine methyl ester (L-NAME) and aminoguanidine (AG) in rats with thioacetamide (TAA)-induced liver fibrosis reversal.

MATERIALS AND METHODS

Male Wistar rats, 230-240 g, received TAA (200 mg kg(-1), intraperitoneally) twice a week for 3 months. Liver resolution was simulated by withdrawal of TAA administration. Thereafter the animals were subdivided into five groups and treated by intragastric intubation with: L-arginine (100 and 300 mg kg(-1)); L-NAME as an inhibitor of both constitutively expressed NOS (eNOS) and inducible NOS (iNOS) (20 mg kg(-1)), AG as a specific inhibitor of iNOS (100 mg kg(-1)) or placebo. The severity of liver fibrosis was assessed by morphometric evaluation of liver slides stained with Azan-Mallory, hydroxyproline (Hyp) determination and mRNA steady state levels of collagen I, transforming growth factor (TGF)-beta1, metalloproteinases (MMP)-13, -14, tissue inhibitor of MMP (TIMP)-1 and plasminogen activator inhibitor (PAI)-1 were quantified by real time PCR. The activities of serum marker enzyme, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase, were measured.

RESULTS

TAA treatment during 3 months induced micronodular liver fibrosis with a pronounced deposition of collagen fibres. L-Arginine did not affect this deposition nor did it affect both relative and total liver hydroxyproline content. Both NOS inhibitors significantly increased the square of the liver connective tissue stained by Azan-Mallory and the above parameters characterizing liver hydroxyproline content. Both NOS inhibitors up-regulated procollagen alpha1 (I), MMP-13, TIMP-1 and PAI-1 mRNA expression. The AG effects were more pronounced. than those of L-NAME. AG treatment also increased mRNA expression of TGF-beta1 and PAI-1.

CONCLUSIONS

Both NOS inhibitors developed a clear pro-fibrotic effect in the liver. Aminoguanidine was more fibrotic than L-NAME. Our data suggest a significant anti-fibrotic role for iNOS rather than for eNOS. L-Arginine did not show any anti-fibrotic properties in the TAA-model used.

Mechanisms of hepatic fibrogenesis

Substantial improvements in the treatment of chronic liver disease have accelerated interest in uncovering the mechanisms underlying hepatic fibrosis and its resolution. Activation of resident hepatic stellate cells into proliferative, contractile, and fibrogenic cells in liver injury remains a dominant theme driving the field. However, several new areas of rapid progress in the past 5-10 years also have taken root, including: (1) identification of different fibrogenic populations apart from resident stellate cells, for example, portal fibroblasts, fibrocytes, and bone-marrow-derived cells, as well as cells derived from epithelial mesenchymal transition; (2) emergence of stellate cells as finely regulated determinants of hepatic inflammation and immunity; (3) elucidation of multiple pathways controlling gene expression during stellate cell activation including transcriptional, post-transcriptional, and epigenetic mechanisms; (4) recognition of disease-specific pathways of fibrogenesis; (5) re-emergence of hepatic macrophages as determinants of matrix degradation in fibrosis resolution and the importance of matrix cross-linking and scar maturation in determining reversibility; and (6) hints that hepatic stellate cells may contribute to hepatic stem cell behavior, cancer, and regeneration. Clinical and translational implications of these advances have become clear, and have begun to impact significantly on the management and outlook of patients with chronic liver disease.

Tetrathiomolybdate protects against bile duct ligation-induced cholestatic liver injury and fibrosis

Tetrathiomolybdate (TM), a potent copper-chelating drug, was initially developed for the treatment of Wilson's disease. Our working hypothesis is that the fibrotic pathway is copper-dependent. Because biliary excretion is the major pathway for copper elimination, a bile duct ligation (BDL) mouse model was used to test the potential protective effects of TM. TM was given in a daily dose of 0.9 mg/mouse by means of intragastric gavage 5 days before BDL. All the animals were killed 5 days after surgery. Plasma liver enzymes and total bilirubin were markedly decreased in TM-treated BDL mice. TM also inhibited the increase in plasma levels of tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta1 seen in BDL mice. Cholestatic liver injury was markedly attenuated by TM treatment as shown by histology. Hepatic collagen deposition was significantly decreased, and it was paralleled by a significant suppression of hepatic smooth muscle alpha-actin and fibrogenic gene expression in TM-treated BDL mice. Although the endogenous antioxidant ability was enhanced, oxidative stress as shown by malondialdehyde and 4-hydroxyalkenals, hepatic glutathione/oxidized glutathione ratio, was not attenuated by TM treatment, suggesting the protective mechanism of TM may be independent of oxidative stress. In summary, TM attenuated BDL-induced cholestatic liver injury and fibrosis in mice, in part by inhibiting TNF-alpha and TGF-beta1 secretion. The protective mechanism seems to be independent of oxidative stress. Our data provide further evidence that TM might be a potential therapy for hepatic fibrosis.

Epithelial expression of TIMP-1 does not alter sensitivity to bleomycin-induced lung injury in C57BL/6 mice

Matrix metalloproteinases (MMPs) are mediators of lung injury, and their activity has been associated with the development of pulmonary fibrosis. To understand how MMPs regulate the development of pulmonary fibrosis, we examined MMP expression in two strains of mice with differing sensitivities to the fibrosis-inducing drug bleomycin. After a single intratracheal injection of the drug, bleomycin-sensitive C57BL/6 mice showed increased expression for MMPs (-2, -7, -9, -13) at both 7 and 14 days posttreatment compared with the bleomycin-resistant BALB/c strain. In addition, TIMP-1, an endogenous inhibitor of MMPs, was upregulated in the lungs of C57BL/6 mice but not BALB/c mice. We designed two strategies to decrease MMP expression to potentially decrease sensitivity of C57BL/6 mice: 1) we engineered C57BL/6 mice that overexpressed TIMP-1 in their lungs via surfactant protein C (SP-C) promoter; and 2) we inhibited expression of MMPs independent of TIMP-1 by knocking out metallothionein (MT), a critical zinc binding protein. SP-C-TIMP-1 mice reduced MMP expression in response to bleomycin. However, they were equally sensitive to bleomycin as their wild-type counterparts, displaying similar levels of hydroxyproline in the lung tissue. MT null mice displayed decreased lung activity of MMPs with no change in TIMP-1. Nonetheless, there was no difference between the MT null and wild-type control littermates with regards to any of the lung injury parameters measured. We conclude that although TIMP-1 expression is differentially regulated in fibrosis-sensitive and fibrosis-resistant strains, epithelial overexpression of TIMP-1 does not appear to substantially alter fibrotic lung disease in mice.

Hepatic stellate cells: protean, multifunctional, and enigmatic cells of the liver

The hepatic stellate cell has surprised and engaged physiologists, pathologists, and hepatologists for over 130 years, yet clear evidence of its role in hepatic injury and fibrosis only emerged following the refinement of methods for its isolation and characterization. The paradigm in liver injury of activation of quiescent vitamin A-rich stellate cells into proliferative, contractile, and fibrogenic myofibroblasts has launched an era of astonishing progress in understanding the mechanistic basis of hepatic fibrosis progression and regression. But this simple paradigm has now yielded to a remarkably broad appreciation of the cell's functions not only in liver injury, but also in hepatic development, regeneration, xenobiotic responses, intermediary metabolism, and immunoregulation. Among the most exciting prospects is that stellate cells are essential for hepatic progenitor cell amplification and differentiation. Equally intriguing is the remarkable plasticity of stellate cells, not only in their variable intermediate filament phenotype, but also in their functions. Stellate cells can be viewed as the nexus in a complex sinusoidal milieu that requires tightly regulated autocrine and paracrine cross-talk, rapid responses to evolving extracellular matrix content, and exquisite responsiveness to the metabolic needs imposed by liver growth and repair. Moreover, roles vital to systemic homeostasis include their storage and mobilization of retinoids, their emerging capacity for antigen presentation and induction of tolerance, as well as their emerging relationship to bone marrow-derived cells. As interest in this cell type intensifies, more surprises and mysteries are sure to unfold that will ultimately benefit our understanding of liver physiology and the diagnosis and treatment of liver disease.

Curcumin protects the rat liver from CCl4-caused injury and fibrogenesis by attenuating oxidative stress and suppressing inflammation

We previously demonstrated that curcumin, a polyphenolic antioxidant purified from turmeric, up-regulated peroxisome proliferator-activated receptor (PPAR)-gamma gene expression and stimulated its signaling, leading to the inhibition of activation of hepatic stellate cells (HSC) in vitro. The current study evaluates the in vivo role of curcumin in protecting the liver against injury and fibrogenesis caused by carbon tetrachloride (CCl(4)) in rats and further explores the underlying mechanisms. We hypothesize that curcumin might protect the liver from CCl(4)-caused injury and fibrogenesis by attenuating oxidative stress, suppressing inflammation, and inhibiting activation of HSC. This report demonstrates that curcumin significantly protects the liver from injury by reducing the activities of serum aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, and by improving the histological architecture of the liver. In addition, curcumin attenuates oxidative stress by increasing the content of hepatic glutathione, leading to the reduction in the level of lipid hydroperoxide. Curcumin dramatically suppresses inflammation by reducing levels of inflammatory cytokines, including interferon-gamma, tumor necrosis factor-alpha, and interleukin-6. Furthermore, curcumin inhibits HSC activation by elevating the level of PPARgamma and reducing the abundance of platelet-derived growth factor, transforming growth factor-beta, their receptors, and type I collagen. This study demonstrates that curcumin protects the rat liver from CCl(4)-caused injury and fibrogenesis by suppressing hepatic inflammation, attenuating hepatic oxidative stress and inhibiting HSC activation. These results confirm and extend our prior in vitro observations and provide novel insights into the mechanisms of curcumin in the protection of the liver. Our results suggest that curcumin might be a therapeutic antifibrotic agent for the treatment of hepatic fibrosis.

A novel synthetic oleanolic acid derivative (CPU-II2) attenuates liver fibrosis in mice through regulating the function of hepatic stellate cells

Regulation on the function of the hepatic stellate cells (HSCs) is one of the proposed therapeutic approaches to liver fibrosis. In the present study, we examined the in vitro and in vivo effects of CPU-II2, a novel synthetic oleanolic acid (OLA) derivative with nitrate, on hepatic fibrosis. This compound alleviated CCl4-induced hepatic fibrosis in mice with a decrease in hepatic hydroxyproline (Hyp) content and histological changes. CPU-II2 also attenuated the mRNA expression of alpha-smooth muscle actin (alpha-SMA) and tissue inhibitor of metalloproteinase type 1 (TIMP-1) induced by CCl4 in mice and reduced both mRNA and protein levels of alpha-SMA in HSC-T6 cells. Interestingly, CPU-II2 did not affect the survival of HSC-T6 cells but decreased the expression of procollagen-alpha1 (I) in HSC-T6 cells through down-regulating the phosphorylation of p38 MAPK.

CONCLUSION

CPU-II2 attenuates the development of liver fibrosis rather by regulating the function of HSCs through p38 MAPK pathway than by damaging the stellate cells.

Gene expression profile analysis of the spontaneous reversal of rat hepatic fibrosis by cDNA microarray

Our aim was to gain insight into the gene expression profile during hepatic fibrosis autoreversal. Spontaneous recovery from hepatic fibrosis was created in SD rats by CCl(4) exposure for 8 weeks and then withdrawal for 6 weeks. Then differentially expressed genes during regression of fibrosis were analyzed using cDNA microarray. Results obtained were further subjected to hierarchical clustering and validated by semiquantitative RT-PCR. Expression of Mapk1 and Rps6ka1, which are critical members of the mitogen-activated protein kinase (MAPK) signaling pathway, was also investigated by Northern blot and immunohistochemistry. Microarray hybridization identified 254 genes differentially expressed throughout resolution of fibrosis. Being verified by RT-PCR, up- or down-regulated genes were classified into various groups according to clustering and function: (1) metabolic enzymes, (2) facilitated diffusion proteins/transporters/symporters, (3) gastrointestinal hormones/receptors, (4) lipoproteins/fatty acid binding proteins, (5) transcription factors/nuclear factors, and (6) the MAPK signaling pathway. The mRNA level of Mapk1 increased greatly as hepatic fibrosis reversed. Meanwhile Mapk1 and Rps6ka1 were proven to be expressed in hepatocytes and absent from mesenchymal cells. Six groups of genes exhibit a close relation to the recovery of CCl(4)-induced hepatic fibrosis. The MAPK signaling-dependent pathway, representing one of the gene groups, may contribute to the reversal of hepatic fibrosis.

Genistein modifies liver fibrosis and improves liver function by inducing uPA expression and proteolytic activity in CCl4-treated rats

AIM

To evaluate the effect of genistein on the fibrosis and matrix degradation caused by experimentally induced fibrosis in rats.

METHODS

Hepatic fibrosis was brought about by chronic administration of carbon tetrachloride to rats. To evaluate the effect of genistein on liver fibrosis and function, total collagen content and proteolytic activity in the liver were quantified. Urokinase-type plasminogen activator (uPA) expression during experimental fibrosis was localized by immunohistochemistry. Histopathological changes were evaluated using light and electron microscopy.

RESULTS

Animals with fibrosis and treated with genistein showed an important reduction (73%) in hepatic collagen content as well as an improvement in liver function (p < 0.001). Genistein increased the capacity of the liver to degrade type I collagen and Matrigel (3.1- and 3.7-fold, respectively; p < 0.001) in animals with liver fibrosis. Genistein increased the number of uPA-immunoreactive cells. The increase in the uPA expression correlated with an increase in proteolytic activity. Histological analysis revealed a reduction in the number of fiber septa in pericentral and perisinusoidal areas. Transmission electron micrographs of livers from animals with fibrosis and treated with genistein showed a reduction in the number of hepatic stellate cells activated and a smaller number of collagen fibers.

CONCLUSION

Genistein is able to improve the liver after injury and fibrosis induced by chronic administration of carbon tetrachloride. This finding suggests that genistein has antifibrogenic potential and could therefore be useful for treating chronic liver disease.

Cystamine ameliorates liver fibrosis induced by carbon tetrachloride via inhibition of tissue transglutaminase

AIM: To investigate the anti-fibrosis effect of the tissue transglutaminase (tTG) specific inhibitor cystamine on liver fibrosis.

METHODS: Sixty-eight male Sprague Dawley rats were divided into three groups: normal control, liver fibrosis control and cystamine-treated group. Liver fibrosis was induced by intraperitoneal injection of carbon tetrachloride (CCl₄), and Cystamine was administrated by intraperitoneal injection starting 2 d before the first administration of CCl₄. Animals in each group were further divided into 2 subgroups according to two time points of 4 wk and 8 wk after treatment. Hepatic function, pathological evaluation (semi-quantitative scoring system, SSS) and liver hydroxyproline (Hyp) content were examined. Real-time PCR was used to detect the expression of tTG, smooth muscle alpha actin (α-SMA), tissue inhibitor of metalloproteinase 1 (TIMP-1) and collagen-1 mRNA. The expressions of tTG and α-SMA protein were detected by Western Blotting.

RESULTS: Eight weeks after treatment, the SSS score of liver was significantly less in the cystamine group than that in the fibrosis control group (P < 0.01). The levels of alanine aminotransferase (ALT) and total bile acid (TBA) at the 4 wk and 8 wk time points were decreased in the cystamine group compared with those in fibrosis controls (P < 0.01). Liver hydroxyproline content at the 4 wk and 8 wk time points showed a substantial reduction in the cystamine group compared to fibrosis controls (P < 0.01). The expression of tTG, α-SMA, collagen-1, TIMP-1 mRNA and tTG, as well as α-SMA protein was downregulated in the cystamine group compared to fibrosis controls.

CONCLUSION: Cystamine can ameliorate CCl₄ induced liver fibrosis and protect hepatic function. The possible mechanism is related to the reduced synthesis of the extracellular matrix (ECM) caused by the inhibition of hepatic stellate cell activation and decreased expression of TIMP-1.

Matrix metalloproteinase gene delivery for liver fibrosis

The resolution of advanced liver fibrosis has been recently recognized to be possible, if the causative stimuli are successfully removed. However, whether complete resolution from cirrhosis, the end stage of liver fibrosis, can be achieved is still questionable. Delivery of interstitial collagenases, such as matrix metalloproteinase (MMP)-1, in the liver could be an attractive strategy to treat advanced hepatic fibrosis from the view point that the imbalance between too few interstitial collagenases and too many of their inhibitors is the main obstacle to the resolution from fibrosis. Remodeling of hepatic extracellular matrix by delivered interstitial collagenases also facilitates the disappearance of activated hepatic stellate cells, the main matrix-producing cells in the liver, and promotes the proliferation of hepatocytes. This review will focus on the impact of the gene delivery of MMPs for the treatment of advanced liver fibrosis while discussing other current therapeutic strategies for liver fibrosis, and on the need for the development of a safe and effective delivery system of MMPs.

Blockade of renin-angiotensin system in antifibrotic therapy

Recent studies have shown that the renin-angiotensin system (RAS) plays a pivotal role in liver fibrosis. An intrahepatic RAS is expressed in chronically damaged livers, and angiotensin-II (AT-II) reportedly stimulates contraction and proliferation of the activated hepatic stellate cells (Ac-HSC), and increases the transforming growth factor-beta (TGF-beta) expression through angiotensin type-I receptors (AT1-R). Some studies have demonstrated that the clinically used angiotensin-converting enzyme (ACE) inhibitor (ACE-I), and AT1-R blockers (ARB) significantly attenuated experimental liver fibrosis along with suppression of the Ac-HSC and hepatic TGF-beta expression. Angiotensin-II also stimulates the tissue inhibitor of metalloproteinases-1 (TIMP-1) in a dose- and time-dependent manner via protein kinase-C as an intracellular signaling cascade in the Ac-HSC, and these effects are completely suppressed by ARB. Combination treatment with low-dose interferon (IFN) and ACE-I exerts a stronger inhibitory effect than either single agent on its own. In humans it has been reported that ARB markedly improved the liver fibrosis score and TGF-beta expression in patients with chronic hepatitis C and non-alcoholic steatohepatitis. Serum fibrosis markers also significantly improved by treatment with low-dose IFN and ACE-I in patients with chronic hepatitis C, refractory to IFN monotherapy. Collectively, these data suggest that the interaction between AT-II and AT1-R plays a pivotal role in liver fibrosis development. Because both ACE-I and ARB are widely used in clinical practice without serious side-effects, these drugs in combination with IFN may provide a new strategy for antifibrosis therapy.

Possible inhibitory effect of oral zinc supplementation on hepatic fibrosis through downregulation of TIMP-1: A pilot study

AIM

To investigate the effect of oral zinc supplementation (polaprezinc) for 24 weeks (34 mg/day zinc) on liver fibrosis in patients with advanced chronic liver disease.

METHODS

Various markers of liver fibrosis, and fibrogenic and fibrolytic enzyme activities were measured before and after zinc supplementation in 17 patients with early cirrhosis.

RESULTS

Serum zinc levels were decreased in the patients as compared with healthy controls. No side-effect was noted in any of the patients who received zinc supplementation. Serum levels of zinc increased by up to 156% over baseline levels in the group of patients who took oral zinc for 24 weeks. In patients whose serum zinc levels increased, the serum levels of type IV collagen and the activity of tissue inhibitors of metalloproteinase-1 (TIMP-1) were significantly reduced, but no such change was observed in the other groups of patients, and no other serum markers changed.

CONCLUSION

These results suggest that oral zinc supplement therapy with polaprezinc is safe and may be a novel and useful strategy for antifibrosis therapy in patients with early liver cirrhosis.

Models of liver fibrosis: exploring the dynamic nature of inflammation and repair in a solid organ

Models of liver fibrosis, which include cell culture models, explanted and biopsied human material, and experimental animal models, have demonstrated that liver fibrosis is a highly dynamic example of solid organ wound healing. Recent work in human and animal models has shown that liver fibrosis is potentially reversible and, in specific circumstances, demonstrates resolution with a restoration of near normal architecture. This Review highlights the manner in which studies of models of liver fibrosis have contributed to the paradigm of dynamic wound healing in this solid organ.

Expression of MMPs and TIMPs in liver fibrosis - a systematic review with special emphasis on anti-fibrotic strategies

In liver tissue matrix metalloproteinases (MMPs) and their specific inhibitors (tissue inhibitors of metalloproteinases, TIMPs) play a pivotal role in both, fibrogenesis and fibrolysis. The current knowledge of the pathophysiology of liver fibrogenesis with special emphasis on MMPs and TIMPs is presented. A systematic literature search was conducted. All experimental models of liver fibrosis that evaluated a defined anti-fibrotic intervention in vivo or in vitro considering MMPs and TIMPs were selected. The methodological quality of all these publications has been critically appraised using an objective scoring system and the content has been summarized in a table.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Adult stem cells in progression and therapy of hepatocellular carcinoma

Hepatocellular carcinoma is one of the most aggressive solid tumours associated with poor prognosis. Despite its significance, there is only an elemental understanding of the mechanisms that drive disease pathogenesis, and there are just limited therapy options. The medical community is currently experiencing a wave of enthusiasm for clinical trials, in which adult stem/progenitor cells are used for liver regeneration. This is based on promising results in animal models and encouraging reports from some initial clinical studies. On the other hand, several essential precautions are not being fully addressed. Stem cells may contribute to fibrosis or give rise to hepatic cancer stem cells as a source of hepatocellular carcinoma. This review outlines the current state of knowledge in progression of liver disease and highlights the function of adult stem cells in disease and therapy.

TIMP-1 regulates cell proliferation by interacting with the ninth zinc finger domain of PLZF

The tissue inhibitors of metalloproteinases (TIMPs) are multifunctional proteins that specifically inhibit matrix metalloproteinases (MMPs) and regulate extracellular matrix (ECM) turnover and tissue remodeling. This is directed by forming tightly bound inhibitory complexes with MMPs. Recent years have revealed important differences of various biological activities between TIMP families but molecular mechanisms are not clear. To define the molecular mechanisms of TIMP-1-dependent biological processes, we used TIMP-1 as bait in a yeast two-hybrid screen, along with a human ovary cDNA library. Further characterization revealed the ninth zinc finger domain as an interacting domain of the promyelocytic leukemia zinc finger protein (PLZF). Interaction of PLZF with TIMP-1 in mammalian cells was also confirmed by co-immunoprecipitation and with in vitro binding assays. We investigated whether TIMP-1-mediated anti-apoptotic activity could promote the growth of ovarian cancer in an experimental model system. TIMP-1 treatment was found to be more effective at increasing ovarian cancer growth when compared with PLZF in parallel experiments. Subsequently, the efficacy of a combined treatment with TIMP-1 and PLZF was investigated. In the presence of both of these proteins, TIMP-1 significantly reduced apoptosis induced by PLZF in cervical carcinoma cells. These combined results indicate that TIMP-1 functions as an anti-activator of the transcriptional repressive activity of PLZF.

JunD is a profibrogenic transcription factor regulated by Jun N-terminal kinase-independent phosphorylation

JunD is implicated in the regulation of hepatic stellate cell (HSC) activation and liver fibrosis via its transcriptional regulation of the tissue inhibitor of metalloproteinases-1 (TIMP-1) gene. In the present study we found in vivo evidence of a role for JunD in fibrogenesis. Expression of JunD was demonstrated in alpha-SMA-positive activated HSCs of fibrotic rodents and human livers. The junD-/- mice were protected from carbon tetrachloride-induced fibrosis. The livers of injured junD-/- mice displayed significantly reduced formation of fibrotic crosslinked collagen and a smaller number of alpha-SMA-positive HSCs compared with those of wild-type (wt) mice. Hepatic TIMP-1 mRNA expression in injured junD-/- mice was 78% lower and in culture activated junD-/- HSCs was 50%-80% lower than that in wt mice. In examining the signal transduction mechanisms that regulate JunD-dependent TIMP-1 expression, we found a role for phosphorylation of the Ser100 residue of JunD but ruled out JNK as a mediator of this event, suggesting ERK1/2 is utilized. In conclusion, a signaling pathway for the development of fibrosis involves the regulation of TIMP-1 expression by phosphorylated JunD.

How variable are hydroxyproline determinations made in different samples of the same liver?

OBJECTIVES

The haphazard distribution of fibrous tissue can interfere with quantitative methods for evaluating hepatic fibrosis. Inter-sample variation may represent a crucial issue when hydroxyproline measurement is used to quantify fibrosis. A comparative study of the hydroxyproline levels in normal and fibrotic rats is herein reported.

MATERIAL AND METHODS

Twelve normal and 20 Capillaria hepatica-infected Wistar rats were used. Two fragments of the liver (A and B) of each rat were taken from separate areas and hydroxyproline measurements were made. Calculated differences in hydroxyproline measurements between samples from the same liver were analyzed by BOOTSTRAP.

RESULTS

Differences in normal rats varied from 0.026 to 1.85 micromol of HP/g, in ten rats, the difference was less than 0.50 micromol. In infected rats, it varied from 0.04 to 2.86 micromol HP/g. Differences higher than 0.69 micromol/g were significant for normal rats (p<0.05) and above 1.22 micromol/g (p<0.05) for fibrotic rats.

CONCLUSIONS

Hydroxyproline ratio in a normal liver kept a fair degree of reproducibility. In the presence of hepatic fibrosis, the levels of hydroxyproline may vary significantly between samples from a single liver and may have limited value in quantifying the extent of fibrosis.

New therapies in hepatitis C virus and chronic liver disease: antifibrotics

Fibrotic liver disease occurs after any of the various forms of injury to the liver. Fibrosis is a critical factor leading to hepatic dysfunction and portal hypertension and its complications. The fibrogenic cascade is complex but leads to accumulation of extracellular matrix proteins, followed by nodular fibrosis, tissue contraction, and alteration in blood flow. A critical concept emerging is that activation of effector cells, which produce extracellular matrix, underlies the fibrogenic process. The aggregate data has not only helped lead to an understanding of the pathophysiologic basis of hepatic fibrogenesis, but it has also provided an important context with which to base novel antifibrotic therapy.

Resolving fibrosis in the diseased liver: translating the scientific promise to the clinic

Liver fibrosis and its end-stage disease cirrhosis are a major cause of mortality and morbidity throughout the world. Fibrosis is a response to chronic liver injury or infection that if unabated leads to the replacement of normal functional liver tissue with scar tissue. Basic research over the past decade has generated a vastly improved knowledge of the cell and molecular biology of liver fibrosis that provides a framework on which to design and develop therapeutics. The field has also witnessed a genuine paradigm shift from the original dogma that liver fibrosis is only ever a progressive process, to the new understanding that liver fibrosis even in an advanced stage can be reversible. There is therefore renewed optimism that liver fibrosis may be cured providing that we develop therapies that halt the fibrogenic process and encourage the natural regenerative properties of the liver. The key to the design of effective therapeutics will be to exploit the ongoing discoveries pertaining to the biology and function of fibrogenic hepatic myofibroblasts and their interplay with other liver cells and with the hepatic extracellular matrix. This review provides a critique of those discoveries in basic research that provide the most promise for translation to the clinic. In addition, we review the latest developments in the search for minimal invasive diagnostic tests for fibrosis that will be essential for determining the efficacy of anti-fibrotic drugs.

Thalidomide prevents rat liver cirrhosis via inhibition of oxidative stress

This study investigated the effect of thalidomide on oxidative stress in rat liver cirrhosis. The cirrhosis of rat was induced by intraperitoneal injection of carbon tetrachloride thrice weekly; meanwhile, thalidomide (10mg/kg or 100mg/kg) was given daily by intragastric administration for 8 weeks. The content of oxidative stress parameters, including superoxide dismutase, glutathione peroxidase, and malondialdehyde, in the liver was detected by biochemical assay. Immunohistochemistry revealed alpha-smooth muscle actin (alpha-SMA), desmin, and tissue inhibitor of metalloproteinase-1 (TIMP-1) protein in the liver. Nuclear factor kappa B p65 (NF-kappaBp65) protein in nucleus and transforming growth factor beta1 (TGF-beta1) protein in cytoplasm were detected by Western blot. NF-kappaBp65, TGF-beta1, and TIMP-1 mRNA levels in the liver were studied using reverse transcriptase polymerase chain reaction. Liver histopathology was significantly improved in rats given high doses of thalidomide. The content of oxidative stress parameters and the expressions of NF-kappaBp65, TGF-beta1 and TIMP-1 protein, and mRNA were significantly decreased in these animals. The expressions of alpha-SMA and Desmin protein were also significantly decreased in them. Thalidomide might exert an effect on the inhibition of oxidative stress via downregulation of NF-kappaB signaling pathway to prevent the progression of liver cirrhosis.

Loss of MMP 13 attenuates murine hepatic injury and fibrosis during cholestasis

Cholestasis occurs in a variety of clinical settings and often results in liver injury and secondary biliary fibrosis. Several matrix metalloproteinases (MMPs) are upregulated in the liver during cholestasis. The function of the major interstitial collagenase, MMP-13, in the initial phase of liver fibrosis is unknown. The aim of this study was to evaluate the role of MMP-13 during the development of cholestasis-induced liver fibrosis by comparing wild-type and MMP-13-deficient mice. Cholestasis was induced by bile duct ligation (BDL) for 5 days or 3 weeks. Activation and proliferation of hepatic stellate cells (HSCs) were detected by immunohistochemistry. Expression of MMP-13 mRNA increased significantly in BDL livers of WT mice. After BDL for 3 weeks liver fibrosis was suppressed in MMP-13-deficient mice versus WT animals. Activation and proliferation of HSCs were also suppressed in livers of MMP-13-deficient mice after BDL. To clarify the mechanism of this suppression, samples from 5-day BDL mice were used for evaluation of liver injury. Compared with those in WT animals, serum ALT and the number of hepatic neutrophils were reduced in MMP-13-deficient mice. Increased expression of the mRNA of inflammatory mediators such as tumor necrosis factor-alpha (TNF-alpha) was significantly suppressed in livers of MMP-13-deficient mice. Upregulation of fibrogenic markers, for example, transforming growth factor beta1 (TGF-beta1), was also significantly suppressed in livers of MMP-13-deficient mice versus in WT mice. In conclusion, distinct from the known function of interstitial collagenase to reduce liver fibrosis by degrading the extracellular matrix, MMP-13 contributes to accelerating fibrogenesis in cholestatic livers by mediating the initial inflammation of the liver.

Reversal of fibrosis: no longer a pipe dream?

The reversal of liver fibrosis is not a new phenomenon. Treatment of the primary disease remains the most effective strategy, but new approaches to promote resolution of fibrosis are being built on the foundations that were provided by research into the basic mechanisms of fibrogenesis. A return to normal hepatic architecture from advanced fibrosis is achievable in some cases, and cirrhosis itself may be partly remediable.

Hepatic fibrosis, stellate cells, and portal hypertension

Hepatic fibrogenesis is the common result of injury to the liver. It is believed to be a critical factor that leads to hepatic dysfunction and may be important in portal hypertension. The fibrogenic response is a complex process in which accumulation of extracellular matrix proteins, tissue contraction, and alteration in blood flow are prominent. A critical event in fibrogenesis is activation of resident perisinusoidal cells that are termed "hepatic stellate cells". Stellate cell activation is characterized by many important phenotypes, including enhanced extracellular matrix synthesis and prominent contractility. Given the central role of stellate cell activation in hepatic fibrogenesis (and portal hypertension), effective therapy for hepatic fibrogenesis is most likely will be directed at this event.

Novel functions of TIMPs in cell signaling

Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of matrix metalloproteinases (MMPs) and the balance between MMPs/TIMPs regulates the extracellular matrix (ECM) turnover and remodeling during normal development and pathogenesis. Increasing evidence indicates a much more complex role for TIMPs during tumor progression and angiogenesis, in addition to their regulation of MMP-mediated ECM degradation. In this article, we review both the MMP-dependent and -independent actions of TIMPs for the regulation of cell death, cell proliferation, and angiogenesis, with a particular emphasis on TIMP-1 in the regulation of tetraspanin/integrin-mediated cell survival signal transduction pathways.

TIMP-1 regulation of cell cycle in human breast epithelial cells via stabilization of p27(KIP1) protein

Increasing evidence suggests that tissue inhibitor of metalloproteinases-1 (TIMP-1) can directly regulate cell growth and apoptosis independent of its matrix metalloproteinases (MMPs)-inhibitory activity. While TIMP-1's antiapoptotic activity has been well demonstrated, conflicting data has been reported regarding TIMP-1's role in growth regulation. Here we show that TIMP-1 reduces the growth rate of human breast epithelial (MCF10A) cells by inducing cell cycle arrest at G(1). TIMP-1-mediated cell cycle arrest is associated with its downregulation of cyclin D(1) and upregulation of p27(KIP1), resulting in inhibition of cyclin-dependent kinase activity necessary for phosphorylation of the tumor suppressor retinoblastoma protein. We further show that TIMP-1 modulation of cyclin D(1) and p27(KIP1) is achieved through TIMP-1-mediated differential regulation of protein stability independent of growth factor signaling. We also show that TIMP-1-mediated differential regulation of cyclin D(1) and p27(KIP1) is independent of cell adhesion signaling. Whereas approximately 50% of MCF10A cells with reduced TIMP-1 expression underwent cell death following loss of cell adhesion (anoikis), TIMP-1 overexpressing cells remained viable with prominent cell cycle arrest without detectable cell death. Taken together, we propose that TIMP-1-mediated cell survival independent of cell adhesion is accompanied with cell cycle arrest in human breast epithelial cells, although cell cycle regulation may not be a prerequisite for TIMP-1 regulation of apoptosis in general.

Tissue inhibitor of metalloproteinase 1 regulates matrix metalloproteinase activity during newt limb regeneration

Matrix metalloproteinase (MMP) activity is important for newt limb regeneration. In most biological processes that require MMP function, MMP activity is tightly controlled by a variety of mechanisms, including the coexpression of natural inhibitors. Here, we show that gene expression of one such inhibitor, tissue inhibitor of metalloproteinase 1 (NvTIMP1), is upregulated during the wound healing and dedifferentiation stages of regeneration when several MMPs are at their maximal expression levels. Newt MMPs and NvTIMP1 also exhibit similar spatial expression patterns during the early stages of limb regeneration. NvTIMP1 inhibits the proteolytic activity of regeneration-related newt MMPs and, like human TIMP1, can induce a weak mitogenic response in certain cell types. These results suggest that NvTIMP1 may be functioning primarily to maintain optimal levels of MMP activity during the early stages of limb regeneration, while possibly serving a secondary role as a mitogen.

Increased ADAMTS-13 proteolytic activity in rat hepatic stellate cells upon activation in vitro and in vivo

INTRODUCTION

ADAMTS-13 is a member of A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS) family, primarily synthesized in hepatic stellate cells (HSCs), one of the major cell types transdifferentiating into myofibroblasts during liver fibrosis. However, the association between ADAMTS-13 expression and HSC activation or liver fibrosis is not known.

METHODS

In this study, we determined the ADAMTS-13 mRNA, protein, and activity in isolated primary HSCs upon activation on a plastic dish and in liver after administration of carbon tetrachloride (CCl(4)) in rats.

RESULTS

We showed that ADAMTS-13 antigen and proteolytic activity in the activated rat HSCs were dramatically increased, whereas ADAMTS-13 mRNA in these cells was only minimally altered. Similarly, the ADAMTS-13 antigen and proteolytic activity in rat liver after CCl(4) injury were also significantly increased, whereas the ADAMTS-13 mRNAs in these liver tissues were only slightly increased compared with normal. Surprisingly, despite the dramatic up-regulation of ADAMTS-13 protein synthesis in the activated HSCs after CCl(4) administration, the plasma levels of ADAMTS-13 protease in rats did not increase concordantly.

CONCLUSION

We conclude that the up-regulation of ADAMTS-13 protein expression in rat HSCs during activation in vitro and in vivo suggests the possibility of ADAMTS-13 proteolysis, an important part of function of the activated HSCs, perhaps through modulation of liver regeneration or formation of liver fibrosis after various injuries. The data also suggest the minimal contribution of the activated HSCs in regulation of plasma levels of ADAMTS-13 protease.

Inhibition of hepatic fibrogenesis by matrix metalloproteinase‐9 mutants in mice

Tissue inhibitor of metalloproteinases-1 (TIMP-1) plays a crucial role in the pathogenesis of hepatic fibrosis and thus may represent an important therapeutic target in the design of anti-fibrotic strategies for chronic liver disease. We present an innovative therapy based on the assignment of inactivated enzymes acting as scavengers for TIMP-1. Hepatic fibrosis was induced in BALB/c mice by repetitive intraperitoneal CCl4 injection. The animals were treated with proteolytic inactive matrix metalloproteinase-9 mutants (E402Q, H401A, E402H/H411E) using adenovirus-mediated gene transfer. Application of these MMP-9 mutants inhibited fibrogenesis, which was indicated by decreasing portal and periportal accumulation of collagen. Total hydroxyproline of liver tissue, the morphometric stage of fibrosis as well as mRNA expression of marker proteins for hepatic fibrosis in livers of E402Q- and H401A-treated mice were significantly reduced. MMP-9 mutants suppressed transdifferentiation of hepatic stellate cells to the myofibroblast like phenotype in vitro and in vivo. Moreover, adenoviral application of the mutants MMP-9-H401A and -E402Q led to increased apoptosis of activated hepatic stellate cells, thought to be the main promoters of hepatic fibrosis. Application of MMP-9 mutants as TIMP-1 scavengers may provide a new therapeutic strategy for hepatic fibrosis.

The role and regulation of hepatic stellate cell apoptosis in reversal of liver fibrosis

Liver fibrosis and its end-stage disease cirrhosis are major world health problems arising from chronic injury of the liver by a variety of etiological factors including viruses, alcohol and drug abuse, the metabolic syndrome, autoimmune disease and hereditary disorders of metabolism. Fibrosis is a progressive pathological process in which wound-healing myofibroblasts of the liver respond to injury by promoting replacement of the normal hepatic tissue with a scar-like matrix composed of cross-linked collagen. Until recently it was believed that this process was irreversible. However emerging experimental and clinical evidence is starting to show that even cirrhosis is potentially reversible. Key to this is the discovery that reversion of fibrosis is accompanied by clearance of hepatic stellate cells (HSC) by apoptosis. Furthermore, proof-of-concept studies in rodents have demonstrated that experimental augmentation of HSC apoptosis will promote the resolution of fibrosis. Consequently there is now considerable interest in determining the molecular events that regulate HSC apoptosis and the discovery of drugs that will stimulate HSC apoptosis in a selective manner. This review will consider the regulatory role played by growth factors (e.g. NGF, IGF-1, TGFbeta), death receptor ligands (TRAIL, FAS), components and regulators of extracellular matrix (integrins, collagen, matrix metalloproteinases and their tissue inhibitors) and signal transduction proteins and transcription factors (Rho/Rho kinase, Jun N-terminal Kinase (JNK), IkappaKinase (IKK), NF-kappa B). The potential for known pharmacological agents such as gliotoxin, sulfasalazine, benzodiazepine ligands, curcumin and tanshinone I to induce HSC apoptosis and therefore to be used therapeutically will be explored.

Molecular pathogenesis of alcohol-induced hepatic fibrosis

Alcohol abuse is a main cause of liver fibrosis and cirrhosis in the western world. Although the major mechanisms of fibrogenesis are independent of the origin of liver injury, alcoholic liver fibrosis features distinctive characteristics, including the pronounced inflammatory response of immune cells due to elevated gut-derived endotoxin plasma levels, increased formation of reactive oxygen species (ROS), ethanol-induced pericentral hepatic hypoxia or formation of cell-toxic and pro-fibrogenic ethanol metabolites (e.g., acetaldehyde or lipid oxidation products). These factors are together responsible for increased hepatocellular cell death and activation of hepatic stellate cells (HSCs), the key cell type of liver fibrogenesis. To date, removing the causative agent is the most effective intervention to prevent the manifestation of liver cirrhosis. A novel experimental approach in fibrosis therapy is the selective induction of cell death in HSCs. Substances such as gliotoxin, anandamide or antibody against tissue inhibitor of metalloproteinase (TIMP)-1 can selectively induce cell death in activated HSCs. These new results in basic science are encouraging for the search of new antifibrotic treatment.

Therapeutic implications of the specific inhibition of causative matrix metalloproteinases in experimental colitis induced by dextran sulphate sodium

Extracellular matrix dynamics, crucial for tissue remodelling, are highly regulated by a cascade of matrix metalloproteinases (MMPs) during inflammation and wound healing processes in inflammatory bowel disease (IBD). Contrary to expectations, there are limited reports to date that MMP inhibitors have some beneficial therapeutic effects in experimental colitis models. Furthermore, clinical trials of MMP inhibitors against certain tumours have failed to show any therapeutic benefit. One major reason for this lack of success may be the apparent uncertainty about the precise spectrum of inhibitory activity required. Since tumour necrosis factor alpha (TNFalpha), a key mediator in colonic inflammation, promotes MMP production in a dose-dependent manner, the therapeutic success of anti-TNFalpha agents against IBD motivated us to re-evaluate the therapeutic potential of MMP inhibition. First, using a quantitative polymerase chain reaction (PCR), western blotting, and zymography, we determined which MMPs were relevant to experimental colitis induced in mice by dextran sulphate sodium. Next, we examined a distinct role for MAPK and NFkappaB signalling pathways in the regulation of the expression of these MMP genes. Finally, we examined whether transcriptional regulation of these MMPs, either indirectly using inhibitors of MAPK and/or NFkappaB signalling pathways or directly using siRNA directed against these MMPs, contributes to the prevention of colitis. Changes in the expression level of colonic MMP-3 and MMP-10 preceded the clinical course of colitis. Colitis improved in mice that received these signal inhibitors, together with suppression of MMP expression. Moreover, siRNA that targeted MMP-3 and MMP-10 effectively reduced both the transcription of these MMPs and the severity of colitis. We conclude that MMP-3 and MMP-10 play a causal role in excess tissue destruction in colitis. Specific inhibition of these MMPs should provide novel therapeutics against IBD.

Mdr2 (Abcb4)-/- mice spontaneously develop severe biliary fibrosis via massive dysregulation of pro- and antifibrogenic genes

BACKGROUND/AIMS

Mdr2 (Abcb4)-/- mice develop hepatic lesions resembling primary sclerosing cholangitis. Our aim was to characterize the evolution of fibrosis in Mdr2-/- mice.

METHODS

Mdr2-/-mice and their wild-type littermates were sacrificed at 2, 4 and 8 weeks after birth. Hepatic collagen was determined biochemically. Fibrosis related transcript levels were quantified from livers by real-time RT-PCR, and MMP activities determined by substrate assays. Liver histology was assessed by connective tissue staining and immunohistochemistry for alpha-smooth muscle actin (alpha-SMA).

RESULTS

Mdr2-/- mice demonstrated a time-dependent increase of relative and total hepatic collagen (fivefold at 8 weeks, compared to wildtype controls), and maximal alpha-SMA immunoreactivity at 4 weeks. Compared to wildtype controls profibrogenic mRNA levels for procollagen alpha1(I), TGFbeta1, TGFbeta2, MMP-2 and -13, TIMP-1, PDGFbeta receptor, and PAI-1 were upregulated up to 27-fold. Most transcripts peaked at 4 weeks, but procollagen alpha1(I) mRNA increased steadily, TIMP-1 mRNA was constantly elevated (20-fold), MMP-13 mRNA was suppressed and interstitial collagenase and gelatinase activities were downregulated.

CONCLUSIONS

Mdr2-/- mice spontaneously progress to severe biliary fibrosis. This is due to a characteristic temporal pattern of upregulated profibrogenic and downregulated fibrolytic genes and activities. These mice are an attractive model to test potential antifibrotics for the treatment of (biliary) liver fibrosis.

Glycyrrhizin down-regulates expression of tissue inhibitor of metalloproteinases-1

AIM: To investigate the regulatory effect of glycyrrhizin on the tissue inhibitor of metalloproteinases-1(TIMP-1) expression and to explore its anti-fibrosis mechanism.

METHODS: The TIMP-1 promoter was amplified by polymerase chain reaction(PCR), and the product was named TIMP-1P. The TIMP-1P was cloned into pGEM-Teasy vector to obtain pGEM-Teasy-TIMP-1P, and then the product and pCAT3-basic vector were digested by NheI and XhoI to construct pCAT3-TIMP-1P. Then pCAT3-TIMP-1P was transfected into HepG2 cells and the cells were treated with 0.1 mmol glycyrrhizin for 48 h. The HepG2 cells transfected with pCAT3-basic were used as negative controls. The expression level of chloramphenicol acetyltransferase(CAT) in HepG2 cells was detected by enzyme-linked immunoassay (ELISA).

RESULTS: The expressive vector pCAT3-TIMP-1P was constructed and confirmed by restriction enzyme digestion and sequencing. The optical density(OD) of the cells transfected with pCAT3-TIMP-1P was significantly higher than that with pCAT3-basic(2.329±0.685 vs 0.004±0.002, F =26.075, P < 0.05). After treatment with glycyrrhizin, the expression of CAT in the HepG2 cells transfected with pCAT3-TIMP-1P was notably decreased as compared with that in the same cells without glycyrrhizin treatment(OD: 0.268±0.009 vs 0.490±0.153, F =35.775, P < 0.05).

CONCLUSION: Glycyrrhizin can down-regulate the activity of TIMP-1 gene promoter as well as inhibit the expression of TIMP-1.

Mechanisms of liver fibrosis

Liver fibrosis represents a significant health problem worldwide of which no acceptable therapy exists. The most characteristic feature of liver fibrosis is excess deposition of type I collagen. A great deal of research has been performed to understand the molecular mechanisms responsible for the development of liver fibrosis. The activated hepatic stellate cell (HSC) is the primary cell type responsible for the excess production of collagen. Following a fibrogenic stimulus, HSCs change from a quiescent to an activated, collagen-producing cell. Numerous changes in gene expression are associated with HSC activation including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses in understanding the molecular basis of collagen gene regulation have revealed a complex process offering the opportunity for multiple potential therapeutic strategies. However, further research is still needed to gain a better understanding of HSC activation and how this cell maintains its fibrogenic nature. In this review we describe many of the molecular events that occur following HSC activation and collagen gene regulation that contribute to the fibrogenic nature of these cells and provide a review of therapeutic strategies to treat this disease.

A farnesoid x receptor-small heterodimer partner regulatory cascade modulates tissue metalloproteinase inhibitor-1 and matrix metalloprotease expression in hepatic stellate cells and promotes resolution of liver fibrosis

The farnesoid X receptor (FXR) is expressed by and regulates hepatic stellate cells (HSCs). In the present study, we investigated whether 6-ethyl chenodeoxycholic acid (6-ECDCA or INT-747), a semisynthetic derivative of chenodeoxycholic acid (CDCA), modulates tissue metalloproteinase inhibitor (TIMP)-1 and matrix metalloprotease (MMP)-2 expression/activity in HSCs and in the liver of rats rendered cirrhotic by 4-week administration of CCl(4). Exposure of HSCs to FXR ligands increases small heterodimer partner (SHP) mRNA by 3-fold and reduces basal and thrombin-stimulated expression of alpha1(I)collagen, alpha-smooth muscle actin (alpha-SMA), TIMP-1, and TIMP-2 by approximately 60 to 70%, whereas it increased matrix metalloprotease (MMP)-2 activity by 2-fold. In coimmunoprecipitation, electromobility shift, and transactivation experiments, FXR activation/overexpression caused a SHP-dependent inhibition of JunD binding to its consensus element in the TIMP-1 promoter. Inhibition of TIMP-1 expression by SHP overexpression enhanced the sensitivity of HSCs to proapoptogenic stimuli. Administration of 3 mg/kg 6-ECDCA, but not 15 mg/kg ursodeoxycholic acid, resulted in early (3-5-day) induction of SHP and prevention of early up-regulation of TIMP-1 mRNA induced by CCl(4). In the prevention protocol, 4-week administration of 6-ECDCA reduced alpha1(I)collagen, alpha-SMA, and TIMP-1 mRNA by 60 to 80%, whereas it increased MMP-2 activity by 5-fold. In the resolution protocol, administration of 3 mg/kg 6-ECDCA promoted liver fibrosis resolution and increased the apoptosis of nonparenchyma liver cells. By demonstrating that a FXR-SHP regulatory cascade promotes the development of a quiescent phenotype and increases apoptosis of HSCs, this study establishes that FXR ligands may be beneficial in treatment of liver fibrosis.

Gene expression profile analysis of spontaneous reversion of CCl4-induced hepatic fibrosis in rats

AIM: To screen the differentially expressed gene in the spontaneous reversion of hepatic fibrosis induced by carbon tetrachloride (CCl₄), and to reveal the gene expression profile in this process.

METHODS: Animal model of hepatic fibrosis with spontaneous reversion was created in SD rats by injection of carbon tetrachloride (CCl₄) for 8 weeks and then withdrawing for 6 weeks. The mRNA of liver tissues was extracted at different time spots in the process of reversion. Then cDNA microarray was used to screen the differentially expressed genes. Finally the products were subjected to hierarchical clustering and confirmed by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) of α-synuclein, A-raf, presenilin-2 and β-actin.

RESULTS: Hepatic fibrosis was progressively reversed after stopping injection of CCl₄. All together, there were 254 (21.59%) genes that changed at the transcription level. Meanwhile, 54, 85, 97 and 132 genes were identified differentially expressed in the 8^th, 10^th, 12^th and 14^th week, respectively. After confirmed by RT-PCR, the differentially expressed were associated with metabolic enzymes, ion channels, transcription factors, gastrointestinal hormones and their receptors, mitogen-activated protein kinase (MAPK) and PI3k/Akt signaling pathway.

CONCLUSION: The gene expression profile is significantly changed in the spontaneous recovery of CCl₄-induced hepatic fibrosis. Genes closely related to the spontaneous recovery are associated with metabolic enzymes, transporter/symporter proteins, gastrointestinal hormones/receptors, lipoprotein/fatty acid binding proteins, transcription factor/nuclear factors, and MAPK signal pathway.

Hepatic fibrosis: molecular mechanisms and drug targets

Liver fibrosis is the common response to chronic liver injury, ultimately leading to cirrhosis and its complications, portal hypertension, liver failure, and hepatocellular carcinoma. Efficient and well-tolerated antifibrotic drugs are currently lacking, and current treatment of hepatic fibrosis is limited to withdrawal of the noxious agent. Efforts over the past decade have mainly focused on fibrogenic cells generating the scarring response, although promising data on inhibition of parenchymal injury and/or reduction of liver inflammation have also been obtained. A large number of approaches have been validated in culture studies and in animal models, and several clinical trials are underway or anticipated for a growing number of molecules. This review highlights recent advances in the molecular mechanisms of liver fibrosis and discusses mechanistically based strategies that have recently emerged.

Imatinib mesylate (STI-571) attenuates liver fibrosis development in rats

It is widely recognized that activated hepatic stellate cells (HSC) play a pivotal role in development of liver fibrosis. A platelet-derived growth factor (PDGF) is the most potent mitogen for HSC. The aim of this study was to examine the effect of imatinib mesylate (STI-571, Gleevec), a clinically used PDGF receptor (PDGFR) tyrosine kinase inhibitor, on development of experimental liver fibrosis. The rat model of pig serum-induced hepatic fibrosis was used to assess the effect of daily oral administration of STI-571 on the indexes of fibrosis. STI-571 markedly attenuated development of liver fibrosis and hepatic hydroxyproline and serum fibrosis markers. The number of alpha-smooth muscle actin-positive cells and mRNA expression of alpha2-(I)-procollagen, tissue inhibitor of metalloproteinases-1, and transforming growth factor-beta were also significantly suppressed by STI-571. Our in vitro study showed that STI-571 markedly attenuated PDGF-BB-induced proliferation and migration and alpha-SMA and alpha2-(I)-procollagen mRNA of activated HSC in a dose-dependent manner. STI-571 also significantly attenuated PDGF-BB-induced phosphorylation of PDGFR-beta, MEK1/2, and Akt in activated HSC. Because STI-571 is widely used in clinical practice, it may provide an effective new strategy for antifibrosis therapy.