Inhibition of apoptosis of activated hepatic stellate cells by tissue inhibitor of metalloproteinase-1 is mediated via effects on matrix metalloproteinase inhibition: implications for reversibility of liver fibrosis

Screening of genes trans-regulated by NS5ATP9 with cDNA microarray assay

AIM: To screen the genes trans-regulated by NS5ATP9 with cDNA microarray assay.

METHODS: The recombined expressive plasmid pcDNA 3.1(-)-NS5ATP9 was constructed, and HepG2 cells were transfected. Total mRNA was isolated from the HepG2 cells transfected with pcDNA3.1(-) and pcDNA3.1(-)-NS5ATP9, respectively. cDNA microarray was employed for detecting and analyzing of mRNA from both HepG2 cells transfected.

RESULTS: From the microarray assay, 3 genes were found up-regulated, and 13 genes down-regulated. Their encoding proteins were involved in cell signal transduction, cell proliferation, cell apoptosis and differentiation.

CONCLUSION: cDNA microarray technology is successfully used to screen diversity genes expressed by NS5ATP9 in HepG2 cells, which brings some new clues for the study of the function of NS5ATP9.

Halofuginone, an inhibitor of collagen synthesis by rat stellate cells, stimulates insulin-like growth factor binding protein-1 synthesis by hepatocytes

BACKGROUND/AIMS

Halofuginone, an inhibitor of collagen synthesis, prevented and caused resolution of established hepatic fibrosis. A genomic approach in vivo was used to search for additional genes responsible for halofuginone mode of action.

METHODS

Fibrosis was induced in rats by thioacetamide (TAA) and evaluated by collagen type I gene expression and the levels of collagen, tissue inhibitors of metalloproteinases-2 and smooth-muscle actin. Halofuginone was given in the diet. cDNA from liver biopsies was hybridized on Atlas arrays comprising of 588 genes. The results were confirmed by Northern blots and in situ hybridization.

RESULTS

Insulin-like growth factor binding protein-1 (IGFBP-1) was one of the 13 genes differentially expressed in the fibrotic liver after halofuginone treatment. After 2 and 4 weeks, halofuginone prevented the TAA-induced down-regulation of IGFBP-1 gene expression. Halofuginone also prevented the TAA-dependent changes in IGFBP-3 gene expression. Halofuginone affected IGFBP-1 synthesis in rat hepatocytes and cells of hepatocyte origin and caused time- and dose-dependent increases in the IGFBP-1 gene expression and synthesis by HepG2 cells. The IGFBP-1 secreted by HepG2-inhibited stellate cell motility.

CONCLUSIONS

Halofuginone is an anti-fibrotic drug that inhibits collagen synthesis by stellate cells and preventing alteration in the synthesis of IGFBPs by hepatic cells.

Tissue inhibitor of metalloproteinase (TIMP)-1: the TIMPed balance of matrix metalloproteinases in the central nervous system

Astrocytes are intimately involved in the mechanisms of neural injury and repair. They participate in a variety of homeostatic functions and elicit repair responses as balance mechanisms. Currently, there is a growing appreciation of a more active role of astrocytes in neuronal signaling and function. One key homeostatic mechanism of astrocytes in tissue repair is maintained through their production of tissue inhibitors of metalloproteinases (TIMPs). The family of TIMPs (1-4) plays a central regulatory role as inhibitors of matrix metalloproteinases (MMPs), enzymes involved in extracellular matrix maintenance and remodeling. Recently, TIMP-1, the inducible form, has been identified as a multifunctional molecule with divergent functions. It participates in wound healing and regeneration, cell morphology and survival, tumor metastasis, angiogenesis, and inflammatory responses. An imbalance of MMP/TIMP regulation has been implicated in several inflammatory diseases of the central nervous system (CNS). Here we review the conundrums of TIMP-1 regulation in CNS pathophysiology. We propose that astrocyte-TIMP-1 may play an important role in CNS homeostasis and disease. Astrocyte TIMP-1 expression is differentially regulated in inflammatory neurodegenerative diseases and may have significant therapeutic relevance.

N-Cadherin cleavage during activated hepatic stellate cell apoptosis is inhibited by tissue inhibitor of metalloproteinase-1

Apoptosis of hepatic stellate cells (HSC) has previously been shown to occur during spontaneous resolution of experimental liver fibrosis. TIMP-1 has also been shown to have a key role because of its ability to inhibit apoptosis of HSC via matrix metalloproteinase (MMP) inhibition. This has led to further study of novel substrates for MMPs that might impact on HSC survival. N-Cadherin is known to mediate cell-cell contacts in fibroblasts. In this study we demonstrate that N-Cadherin is expressed by activated rat HSC. Furthermore, during apoptosis of HSC, the N-Cadherin is cleaved into smaller fragments. Apoptosis of HSC may be inhibited by TIMP-1. This is associated with reduced fragmentation of N-Cadherin. N-Cadherin may have an important role in supporting HSC survival while N-Cadherin cleavage may play a part in promoting HSC apoptosis in recovery from liver fibrosis.

Expression of TIMP-1 and TIMP-2 in rats with hepatic fibrosis

AIM: To investigate the location and expression of TIMP-1 and TIMP-2 in the liver of normal and experimental hepatic fibrosis in rats.

METHODS: The rat models of experimental immunity hepatic fibrosis (n = 20) were prepared by the means of immunologic attacking with human serum albumin (HSA), and normal rats (n = 10) served as control group. Both immunohistochemistry and in situ hybridization methods were respectively used to detect the TIMP-1 and TIMP-2 mRNA and related antigens in liver. The liver tissue was detected to find out the gene expression of TIMP-1 and TIMP-2 with RT-PCR.

RESULTS: The TIMP-1 and TIMP-2 related antigens in livers of experimental group were expressed in myofibroblasts and fibroblasts (TIMP-1: 482 ± 65 vs 60 ± 20; TIMP-2: 336 ± 48 vs 50 ± 19, P < 0.001). This was the most obvious in portal area and fibrous septum. The positive signals were located in cytoplasm, not in nucleus. Such distribution and location were confirmed by situ hybridization (TIMP-1/β-actin: 1.86 ± 0.47 vs 0.36 ± 0.08; TIMP-2/β-actin: 1.06 ± 0.22 vs 0.36 ± 0.08, P < 0.001). The expression of TIMP-1 and TIMP-2 was seen in the liver of normal rats, but the expression level was very low. However, the expression of TIMP-1 and TIMP-2 in the liver of experimental group was obviously high.

CONCLUSION: In the process of hepatic fibrosis, fibroblasts and myofibroblasts are the major cells that express TIMPs. The more serious the hepatic fibrosis is in the injured liver, the higher the level of TIMP-1 and TIMP-2 gene expression.

4-Hydroxynonenal as a selective pro-fibrogenic stimulus for activated human hepatic stellate cells

BACKGROUND/AIMS

4-Hydroxynonenal (HNE) is a putative pro-fibrogenic product of oxidative stress able to elicit apoptosis and cytotoxicity in several cell types. This study has been performed to evaluate its 'in vivo' levels in injured liver and whether HNE may induce apoptosis and/or affect selected phenotypic responses in activated human hepatic stellate cells (HSC/MF).

METHODS/RESULTS

During the development of acute liver injury induced by CCl(4), liver tissue HNE levels were in the range 0.5-10 microM, as shown by high performance liquid chromatography analysis. Cultured human HSC/MF, developed cytotoxicity only if exposed to very high HNE concentrations (25-50 microM) without any sign of induction of classic, caspase-dependent apoptosis, as assessed by evaluating morphology and biochemical parameters of cell death. HNE, at non-cytotoxic doses, up-regulated procollagen type I and tissue inhibitor of metalloproteinases-1 gene expression and/or protein synthesis without significantly affecting chemotaxis (wound healing and haptotaxis assay), matrix metalloproteinases 1 and 2 mRNA expression and activity as well as basal DNA synthesis.

CONCLUSIONS

HNE, at concentrations compatible with those detected in vivo, does not elicit HSC/MF classic apoptosis but, rather, may act as a potent pro-fibrogenic stimulus for the expression of genes involved in excess extracellular matrix deposition and proposed as survival signals for HSC/MF.

Hepatocytes express nerve growth factor during liver injury: evidence for paracrine regulation of hepatic stellate cell apoptosis

A key feature of recovery from liver fibrosis is hepatic stellate cell (HSC) apoptosis, which serves the dual function of removing the major source of neomatrix and tissue inhibitors of metalloproteinases thereby facilitating matrix degradation. The mechanisms regulating HSC apoptosis remain undefined but may include the interaction of nerve growth factor (NGF) with its receptor, p75, on HSC. In this study, by TaqMan polymerase chain reaction in situ hybridization and immunohistochemistry, we demonstrate that NGF is expressed by hepatocytes during fibrotic injury. Peak hepatocyte expression of NGF (48 hours after CCl(4) injection) coincides with maximal rate of apoptosis of HSC by terminal dUTP nick-end labeling staining. Addition of recombinant NGF to HSC in tissue culture causes a dose-dependent increase in apoptosis. NGF regulates nuclear factor (NF)-kappaB activity, reducing p50/p65 binding detected by electromobility shift assay and reduced NF-kappaB CAT reporter activities from both basal unstimulated levels and after NF-kappaB induction by tumor necrosis factor. In each case, a relative reduction in NF-kappaB binding was associated with a significant increase in caspase 3 activity. These data provide evidence that NGF is expressed during fibrotic liver injury and may regulate number of activated HSCs via induction of apoptosis.

Apoptosis of hepatic stellate cells in carbon tetrachloride induced acute liver injury of the rat: analysis of isolated hepatic stellate cells

BACKGROUND/AIMS

Analysis of isolated hepatic stellate cells (HSCs) from the injured liver may provide direct information on HSC apoptosis. However, it has not been established whether apoptotic HSCs would be isolated using the usual density gradient centrifugation method. The aim of this study was to observe the serial pattern of proliferation and apoptosis in isolated HSCs in comparison with that of liver tissue sections in CCl4 induced acute liver injury.

METHODS

Male Sprague-Dawley rats were treated with a single intraperitoneal injection of carbon tetrachloride (CCl4) and were killed at various time points after the treatment.

RESULTS

HSC proliferation showed a maximal increase at 32 h after CCl4 injection. Apoptosis of HSC, examined by quantitative analysis of annexin-V-fluorescein isothiocyanate (FITC)staining, showed the maximal increase at 64 h. Apoptosis of HSC in liver tissue sections examined by counting desmin and Tdt-mediated-dUTP biotin nick end labeling (TUNEL) double staining cells, peaked at 64 h. The number of TUNEL positive HSCs in liver tissue sections correlated significantly with annexin-V-FITC binding of isolated HSC.

CONCLUSIONS

Studying apoptosis using apoptotic HSCs isolated by a usual density gradient centrifugation method from injured tissue sections would be feasible since it correlated with in vivo apoptosis of HSC.

Characteristic expression profiles induced by genotoxic carcinogens in rat liver

When applied in toxicological studies, the recently developed gene expression profiling techniques using microarrays, which brought forth the new field of toxicogenomics, facilitate the interpretation of a toxic compound's mechanism of action. In this study, we investigated whether genotoxic carcinogens at doses known to induce liver tumors in the 2-year rat bioassay deregulate a common set of genes in a short-term in vivo study and, if so, whether these deregulated genes represent defined biological pathways. Rats were dosed with the four genotoxic hepatocarcinogens dimethylnitrosamine (4 mg/kg/day), 2-nitrofluorene (44 mg/kg/day), aflatoxin B1 (0.24 mg/kg/day), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 20 mg/kg/day). After treatment for up to 14 days, the expression profiles of the livers were analyzed on Affymetrix RG_U34A microarrays. Among the significantly upregulated genes were a set of target genes of the tumor suppressor protein p53, indicating a DNA damage response. Such a response was expected and, therefore, confirmed the validity of our approach. In addition, the gene expression changes suggest a specific detoxification response, the activation of proliferative and survival signaling pathways, and some cell structural changes. These responses were strong throughout the 14 day time course for 2-nitrofluorene and aflatoxin B1; in the case of dimethylnitrosamine and NNK, the effects were weakly detectable at day 1 and then increased with time. For dimethylnitrosamine and aflatoxin B1, which caused observable inflammation in vivo, we found a corresponding upregulation of inflammatory genes at the same time points. Thus, by the toxicogenomic analysis of short-term in vivo studies, we identified genes and pathways commonly deregulated by genotoxic carcinogens, which may be indicative for the early events in tumorigenesis and, thus, predictive of later tumor development.

Unbalanced collagenases/TIMP-1 expression and epithelial apoptosis in experimental lung fibrosis

In this study, we examined the sequential expression of several matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and growth factors as well as the presence of apoptosis in a model of pulmonary fibrosis induced in rats with paraquat and hyperoxia. Animals showing neither clinical nor morphological changes with this double aggression were classified as "resistant". Rats were killed at 1, 2, 3, and 6 wk, and lungs were used for collagen content, gene expression by real-time PCR, gelatinolytic activity by zymography, apoptosis by in situ DNA fragmentation, and protein localization by immunohistochemistry. Our results showed a significant decrease of collagenases MMP-8 and MMP-13, with an increase of TIMP-1 and transforming growth factor-beta. Immunoreactive TIMP-1 was increased in experimental rats and primarily localized in alveolar macrophages. Expression of gelatinases MMP-2 and MMP-9 mRNAs was not affected, but lung zymography revealed an increase in progelatinase B, progelatinase A, and its active form. Epithelial apoptosis was evident from the first week, whereas at later periods, interstitial cell apoptosis was also noticed. Resistant animals behave as controls. These findings suggest that an imbalance between collagenases and TIMPs, excessive gelatinolytic activity, and epithelial apoptosis participate in the fibrotic response in this experimental model.

Involvement of Rho/Rho kinase pathway in regulation of apoptosis in rat hepatic stellate cells

Hepatic stellate cells (HSCs) play a central role in the development of hepatic fibrosis. Recent evidence has revealed that HSCs also play a role in its resolution, where HSC apoptosis was determined. Moreover, induction of HSC apoptosis caused a reduction of experimental hepatic fibrosis in rats. Thus knowing the mechanism of HSC apoptosis might be important to clarify the pathophysiology and establish the therapeutic strategy for hepatic fibrosis. In HSCs, Rho and Rho kinase are known to regulate contraction, migration, and proliferation with modulation of cell morphology. Controversy exists as to the participation of Rho and Rho kinase on cell survival, and little is known regarding this matter in HSCs. In this study, we directed our focus on the role of the Rho pathway in the regulation of HSC survival. C3, an inhibitor of Rho, increased histone-associated DNA fragmentation and caspase 3 activity with enhanced condensation of nuclear chromatin in rat cultured HSCs. Moreover, Y-27632, an inhibitor of Rho kinase, had the same effects, suggesting that inhibition of the Rho/Rho kinase pathway causes HSC apoptosis. On the other hand, lysophosphatidic acid, which stimulates the Rho/Rho kinase pathway, decreased histone-associated DNA fragmentation in HSCs. Inhibition of the Rho/Rho kinase pathway did not affect p53, Bcl-2, or Bax levels in HSCs. Thus we concluded that the Rho/Rho kinase pathway may play a role in the regulation of HSC survival.

Tissue inhibitor of metalloproteinase-1 protects human breast epithelial cells against intrinsic apoptotic cell death via the focal adhesion kinase/phosphatidylinositol 3-kinase and MAPK signaling pathway

Tissue inhibitor of metalloproteinase (TIMP-1) is a natural protease inhibitor of matrix metalloproteinases (MMPs). Recent studies revealed a novel function of TIMP-1 as a potent inhibitor of apoptosis in mammalian cells. However, the mechanisms by which TIMP-1 exerts its anti-apoptotic effect are not understood. Here we show that TIMP-1 activates cell survival signaling pathways involving focal adhesion kinase, phosphatidylinositol 3-kinase, and ERKs in human breast epithelial cells to TIMP-1. TIMP-1-activated cell survival signaling down-regulates caspase-mediated classical apoptotic pathways induced by a variety of stimuli including anoikis, staurosporine exposure, and growth factor withdrawal. Consistently, down-regulation of TIMP-1 expression greatly enhances apoptotic cell death. In a previous study, substitution of the second amino acid residue threonine for glycine in TIMP-1, which confers selective MMP inhibition, was shown to obliterate its anti-apoptotic activity in activated hepatic stellate cells suggesting that the anti-apoptotic activity of TIMP-1 is dependent on MMP inhibition. Here we show that the same mutant inhibits apoptosis of human breast epithelial cells, suggesting different mechanisms of TIMP-1 regulation of apoptosis depending on cell types. Neither TIMP-2 nor a synthetic MMP inhibitor protects breast epithelial cells from intrinsic apoptotic cell death. Furthermore, TIMP-1 enhances cell survival in the presence of the synthetic MMP inhibitor. Taken together, the present study unveils some of the mechanisms mediating the anti-apoptotic effects of TIMP-1 in human breast epithelial cells through TIMP-1-specific signal transduction pathways.

Cloning and expression of tissue inhibitor of metalloproteinases-1 (TIMP-1) gene in Chinese

AIM

To clone the Chinese gene of TIMP-1 and express the fusion protein MBP-TIMP-1.

METHODS

The fragment of TIMP-1 gene from the liver tissue of indigenous Hunan residents was amplified by RT-nest-PCR and it was cloned, sequenced by gene recombinations techniques. Fusion protein MBP-TIMP-1 was expressed in E.coli, analysed by SDS-PAGE and Western blot and purified by affinity chromatography.

RESULTS

The sequence of cloned Chinese TIMP-1 gene was 624 bp. It is homologous with the reported other human TIMP-1 gene sequence. Fusion protein MBP-TIMP-1 was 66 kd and is of the antigenicity of TIMP-1. The MBP-TIMP-1 was purified by affinity chromatography.

CONCLUSION

The Chinese gene of TIMP-1 was cloned and MBP-TIMP-1 was expressed and purified successfully in vitro. It may be useful to the diagnosis of liver fibrosis.

Cathepsin B inactivation attenuates hepatic injury and fibrosis during cholestasis

Although a lysosomal, cathepsin B-dependent (Ctsb-dependent) pathway of apoptosis has been described, the contribution of this pathway to tissue damage remains unclear. Our aim was to ascertain if Ctsb inactivation attenuates liver injury, inflammation, and fibrogenesis after bile duct ligation (BDL). In 3-day BDL mice, hepatocyte apoptosis, mitochondrial cytochrome c release, and serum alanine aminotransferase (ALT) values were reduced in Ctsb-/- versus Ctsb+/+ animals. Likewise, R-3032 (a Ctsb inhibitor) also reduced these parameters in BDL WT mice. Both genetic and pharmacologic inhibition of Ctsb in the BDL mouse reduced (a). hepatic inflammation, as assessed by transcripts for CXC chemokines and neutrophil infiltration, and (b). fibrogenesis, as assessed by transcripts for stellate cell activation and sirius red staining for hepatic collagen deposition. These differences could not be ascribed to alterations in cholestasis. These findings support a prominent role for the lysosomal pathway of apoptosis in tissue injury and link apoptosis to inflammation and fibrogenesis. Ctsb inhibition may be therapeutic in liver diseases.

Cathepsin B inactivation attenuates hepatic injury and fibrosis during cholestasis

Although a lysosomal, cathepsin B-dependent (Ctsb-dependent) pathway of apoptosis has been described, the contribution of this pathway to tissue damage remains unclear. Our aim was to ascertain if Ctsb inactivation attenuates liver injury, inflammation, and fibrogenesis after bile duct ligation (BDL). In 3-day BDL mice, hepatocyte apoptosis, mitochondrial cytochrome c release, and serum alanine aminotransferase (ALT) values were reduced in Ctsb-/- versus Ctsb+/+ animals. Likewise, R-3032 (a Ctsb inhibitor) also reduced these parameters in BDL WT mice. Both genetic and pharmacologic inhibition of Ctsb in the BDL mouse reduced (a). hepatic inflammation, as assessed by transcripts for CXC chemokines and neutrophil infiltration, and (b). fibrogenesis, as assessed by transcripts for stellate cell activation and sirius red staining for hepatic collagen deposition. These differences could not be ascribed to alterations in cholestasis. These findings support a prominent role for the lysosomal pathway of apoptosis in tissue injury and link apoptosis to inflammation and fibrogenesis. Ctsb inhibition may be therapeutic in liver diseases.

Tissue inhibitor of metalloproteinases-1 signalling pathway leading to erythroid cell survival

Tissue inhibitors of metalloproteinases (TIMP) are specific inhibitors of matrix metalloproteinases (MMPs) and thus participate in maintaining the balance between extracellular matrix deposition and degradation in several physio-pathological processes. Nevertheless, TIMP must be regarded as multifunctional proteins involved in cell growth, angiogenesis and apoptosis. The molecular mechanisms induced by TIMP remain largely unknown. In the present study, we provide evidence that TIMP-1 induces a significant anti-apoptotic effect in the human erythroleukaemic cell line UT-7 and in the murine myeloid cell line 32D. Using specific kinases inhibitors, we show that TIMP-1-mediated cell survival is dependent upon Janus kinase (JAK) 2 and phosphoinositide 3-kinase (PI 3-kinase) activities. By transient transfection of dominant-negative Akt in UT-7 cells, we demonstrate that this kinase is crucial for the TIMP-1 anti-apoptotic effect. Moreover, TIMP-1 enhances specific phosphorylation of both Akt and Bad (Bcl-2/Bcl-X(L)-antagonist, causing cell death) in a PI 3-kinase-dependent manner and, besides, controls the level of the anti-apoptotic protein Bcl-X(L). We conclude that TIMP-1 induces haematopoietic cell survival via the JAK2/PI 3-kinase/Akt/Bad pathway.

Effect of caffeic acid phenethyl ester on proliferation and apoptosis of hepatic stellate cells in vitro

AIM

To investigate the role of nuclear factor-kappaB (NF-kappaB) inhibitor caffeic acid phenethy1 ester (CAPE) in the proliferation, collagen synthesis and apoptosis of hepatic stellate cells (HSCs) of rats.

METHODS

The HSCs from rats were isolated and cultured in Dulbecco's Modified Eagle's Medium (DMEM) and treated with CAPE. The proliferation and collagen synthesis of HSCs were determined by (3)H-TdR and (3)H-proline incorporation respectively, and the expression of type I, III procollagen genes was further explored by in situ hybridization. Apoptosis cell indices (AIs) were examined using terminal deoxynucleotidyl transferase- mediated DIG-dUTP nick end labeling (TUNEL).

RESULTS

In activated HSC in culture, CAPE significantly inhibited (3)H-TdR and (3)H-proline incorporation by HSCs at concentrations of 5 micromol/L and 10 micromol/L respectively. CAPE also reduced the type I procollagen gene expression (P<0.05) at higher concentration. Apoptosis of HSC was induced by CAPE and the AIs were time-and dose-dependently increased from 2.82+/-0.73 % to 7.66+/-1.25 % at 12 h (P<0.01) and from 3.15+/-0.88 % to 10.61+/-2.88 % at 24 h (P<0.01).

CONCLUSION

CAPE inhibits proliferation and collagen synthesis of HSC at lower concentration and induces HSC apoptosis at higher concentration.

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Involvement of the electrophile responsive element and p53 in the activation of hepatic stellate cells as a response to electrophile menadione

The cytotoxic effects of menadione and hydrogen peroxide were examined in two hepatic stellate cell lines derived from normal or cirrhotic rat liver. The cirrhotic fat-storing cells (CFSC) were found more resistant than the normal fat-storing cells (NFSC) to menadione cytotoxicity. No significant differences were observed in hydrogen peroxide toxicity in these two cell lines. Although protein levels and enzymatic activities of catalase, Cu,Zn-SOD, Mn-SOD, and NADPH cytochrome c reductase were similar in these cell lines, 20-fold increases of NAD(P)H:quinone oxidoreductase 1 (NQO1) enzymatic activity and protein levels were detected in CFSC compared to those of NFSC. Gel mobility shift assays and functional analysis using transient transfection experiments indicated the involvement of the electrophile responsive element (EPRE) in the up-regulation of the NQO1 expression. Antibody supershift analysis revealed that, although Nrf2 is a member of the EPRE-binding complex in both NFSC and CFSC, Nrf1 was identified as a part of the protein/DNA complex only in CFSC. Expression of p53 tumor suppressor gene was found in higher levels in CFSC than in NFSC. We conclude that activation of the EPRE-signaling pathway, which up-regulates several phase II genes and affects p53 stabilization, may offer resistance to hepatic stellate cells against oxidative damage during hepatic injury. This resistance may be a part of the activation process of the hepatic stellate cells and could contribute to their increased proliferation and production of extracellular matrix.

Effects of hepatocyte growth factor on fibrosis and hepatic expression of MMP-1 andTIMP-1

AIM: To investigate the effect of hepatocyte growth factor (HGF) on severity of liver fibrosis and hepatic expressions of MMP-1, TIMP-1 and to explore the mechanism of HGF in preventing liver fibrosis in rats.

METHODS: Eighty male Wistar rats were randomly divided into normal control group (Group A, 16 rats), liver fibrosis model group (Group B, 54 rats) and HGF therapy group (Group C, 10 rats). The liver fibrosis model was induced by administration CCl₄ intraperitoneally. Rats in Group C had been administered HGF for six weeks and were sacrificed afterwards. Eight rats from each of group A and B were randomly sacrificed on week 6 simultaneously as that in group C. The remaining rats in-group B were randomly further subdivided into liver fibrosis model group (Group D, 12 rats) and HGF therapy group (Group E, 10 rats), HGF was administered to rats in group E on week. 7.All rats in group D and E were sacrificed on week 10.Liver function and levels of serum hyaluronic acid (HA), mucin (LN), collegen type IV (CIV), procollagen III (PCIII) were tested; the expression of MMP-1 and TIMP-1 were determined by immunohistochemical staining and analyzed by computer.

RESULTS: Compared with Group B, the serum levels of ALT, AST, HA, LN, CIV, PCIII in Group C were significantly reduced (P < 0.01), MMP-1 activity was slightly increased (0.25 ± 0.02, vs 0.22 ± 0.05, P < 0.05), TIMP-1 activity was markedly reduced (0.34 ± 0.05, vs 0.45 ± 005, P < 0.01). TIMP-1 activity in Group E (0.31 ± 0.07) was also markedly reduced in comparison with Group D (0.42 ± 0.06) (P < 0.01).

CONCLUSIONS: HGF has obvious effect in preventing development of liver fibrosis; it might facilitate degradation of hepatic fibrosic tissue via increasing the MMP-1 activity and or inhibiting TIMP-1 activity.

Effect of Chinese herb Shuangjiawuling on expression of TIMPs in rat with liver fibrosis

AIM: To explore the effect of Chinese herb Shuangjiawuling in preventing hepatic fibrosis in rat with liver fibrosis.

METHODS: Rat immunogenic liver fibrosis model was induced by administration human serum albumin (HSA 200 g/L) intravenously, 80 rats were randomly divided into 5 groups. Shuangjiawuling was taken orally simultaneously with (group A), immediately after (group B), or 3 months after (group C) administration of HAS intravenously. Colchine tablets were taken orally with the administration of HAS (group D), normal rats were used as control (Group E). The pathological changes of liver tissue were observed by HE and Von-Gieson staining. The hepatic mRNA and protein of TIMP-1 and TIMP-2 were analyzed by in site hybridization and immunohistochemistry.

RESULTS: Hepatic fibrosis developed gradually and became obviously on the third month after administration of HAS. And strong expressions of TIMP-1 and TIMP-2 were observed, however, its expression and hepatic fibrosis were reduced dramatically following administration of Shuangjiawuling and colchine tablets. The effect of Shuangjiawuling in preventing fibrosis was superior to that of colchine tablets (P<0.05), and its effect in group A, B, and C decreased in order.

CONCLUSION: Chinese herb Shuangjiawuling can inhibit the development of hepatic fibrosis and the expression of TIMPs, and promoted the effect of the degradation of the extracellular matrix.

Approaches for treatment of liver fibrosis in chronic hepatitis C

In the past 20 years, the elucidation of the mechanisms responsible for liver fibrogenesis has provided many potential targets for antifibrotic treatments. Difficulty has arisen, however, from the fact that fibrogenesis is part of a general beneficial wound healing process. To be successful, an antifibrotic treatment of HCV might need to be delivered selectively to the hepatic site of fibrogenesis or targeted precisely at an HCV-specific regulatory mechanism. It is likely that in the future, besides viral eradication, another treatment goal in chronic HCV infection will be to reverse existing fibrosis, but considerable work is necessary before making this a reality.

Tissue inhibitor of metalloproteinase 1 inhibits excitotoxic cell death in neurons

The upregulation of TIMP-1 following an excitotoxic injury has recently been hypothesized to be part of a general neuronal response that mediates long-lasting changes involved in tissue reorganization and possibly neuroprotection. In this study we have shown for the first time that within hours of applying TIMP-1 in recombinant form or by adenovirus-mediated gene transfer, neurons are highly protected against excitotoxic injury. Neither TIMP-3 nor a nonsecretable form of TIMP-1 protected neurons. TIMP-1 conferred highly significant protection to hippocampal cells exposed to a wide range of glutamic acid concentrations in both dissociated and organotypic hippocampal cultures. TIMP-1 did not prevent apoptotic cell death or death mediated by chemical ischemia. The observed neuroprotection may be explained by a decrease in calcium influx into neurons following stimulation with glutamate. These findings have a fundamental implication for our understanding of the physiological role of secreted TIMP-1 in the central nervous system.

Emerging concepts in inflammation and fibrosis

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

Developing strategies for liver fibrosis treatment

Liver fibrosis represents a major worldwide healthcare burden. Current therapy is limited to removing the causal agent. This approach is successful in some diseases; particularly haemochromatosis and chronic viral hepatitis. However, for many patients treatment is not possible, while other patients present to medical attention at an advanced stage of fibrosis. There is therefore a great need for novel therapies for liver fibrosis. The hepatic stellate cell has been recognised to be responsible for most of the excess extracellular matrix observed in chronic liver fibrosis. The detailed understanding of hepatic stellate cell biology has allowed the rational design of novel antifibrotic therapies. This review describes for the general reader the novel emerging therapies for liver fibrosis.

Sphingosine 1-phosphate triggers both apoptotic and survival signals for human hepatic myofibroblasts

Hepatic myofibroblasts (hMFs) are central in the development of liver fibrosis during chronic liver diseases, and their removal by apoptosis contributes to the resolution of liver fibrosis. We previously identified Edg receptors for sphingosine 1-phosphate (S1P) in human hMFs. Here, we investigated the effects of S1P on hMF apoptosis. S1P reduced viability of serum-deprived hMFs by an apoptotic process that was unrelated to the conversion of S1P into sphingosine and ceramide. The apoptotic effects of S1P were receptor-independent because dihydro-S1P, an Edg agonist, had no effect. S1P also stimulated a receptor-dependent survival pathway, revealed by enhanced activation of caspase-3 by S1P in the presence of pertussis toxin. Cell survival relied on two pertussis toxin-sensitive events, activation of ERK and activation of phosphatidylinositol 3-kinase (PI3K)/Akt by S1P. Both pathways were also activated by dihydro-S1P. Blunting either ERK or PI3K enhanced caspase-3 stimulation by S1P, and simultaneous inhibition of both pathways resulted in additive effects on caspase-3 activation. In conclusion, S1P induces apoptosis of human hMFs via a receptor-independent mechanism and stimulates a survival pathway following activation of Edg receptors. The survival pathway arises from the sequential activation of G(i)/G(o) proteins and independent stimulations of ERK and PI3K/Akt. Therefore, blocking Edg receptors may sensitize hepatic myofibroblasts to apoptosis by S1P.

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

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