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C-Met confers protection against chronic liver tissue damage and fibrosis progression after bile-duct-ligation in mice

ABSTRACT: The HGF/c-Met system is an essential inducer of hepatocyte growth and proliferation. Although a fundamental role for the HGF receptor c-Met has been demonstrated in acute liver regeneration its cell specific role in hepatocytes during chronic liver injury and fibrosis progression has not been determined yet. In order to better characterize the role of c-Met in hepatocytes we generated a hepatocyte-specific c-Met knockout mouse (c-Met∆hepa) using the Cre-loxP system and studied its relevance after bile-duct ligation. Two strategies for c-Met deletion in hepatocytes were tested. Early deletion during embryonic development was lethal, while post-natal Cre-expression was successful leading to the generation of viable c-Met∆hepa mice. Bile-duct ligation in these mice resulted in extensive necrosis and lower proliferation rates of hepatocytes. Gene array analysis of c-Met∆hepa mice revealed a significant reduction of anti-apoptotic genes in c-Met deleted hepatocytes. These findings could be functionally tested as c-Met∆hepa mice showed a stronger apoptotic response after bile-duct ligation and Jo-2 stimulation. This phenotype was associated with increased expression of pro-inflammatory cytokines (TNF-a and IL-6) and an enhanced recruitment of neutrophils. Activation of these mechanisms triggered a stronger pro-fibrogenic response as evidenced by increased TGF-b1, a-SMA, collagen-1a mRNA expression and enhanced collagen-fiber staining in c-Met∆hepa mice.

ORGANISM(S): Mus musculus

PROVIDER: GSE13992 | GEO | 2009/02/18

SECONDARY ACCESSION(S): PRJNA112489

REPOSITORIES: GEO

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Project description:Extrahepatic cholestasis leads to complex injury and repair processes that result in bile infarct formation, neutrophil infiltration, cholangiocyte and hepatocyte proliferation, extracellular matrix remodeling, and fibrosis. To identify early molecular mechanisms of injury and repair after bile duct obstruction, microarray analysis was performed on liver tissue 24 hours after bile duct ligation (BDL) or sham surgery. The most upregulated gene identified encodes plasminogen activator inhibitor 1 (PAI-1, Serpine 1), a protease inhibitor that blocks urokinase plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) activity. Because PAI-1, uPA, and tPA influence growth factor and cytokine processing as well as extracellular matrix remodeling, we evaluated the role of PAI-1 in cholestatic liver injury by comparing the injury and repair processes in wild-type (WT) and PAI-1-deficient (PAI-1-/-) mice after BDL. PAI-1-/- mice had fewer and smaller bile infarcts, less neutrophil infiltration, and higher levels of cholangiocyte and hepatocyte proliferation than WT animals after BDL. Furthermore, PAI-1-/- mice had higher levels of tPA activation and mature hepatocyte growth factor (HGF) after BDL than WT mice, suggesting that PAI-1 effects on HGF activation critically influence cholestatic liver injury. This was further supported by elevated levels of c-Met and Akt phosphorylation in PAI-1-/- mice after BDL. In conclusion, PAI-1 deficiency reduces liver injury after BDL in mice. These data suggest that inhibiting PAI-1 might attenuate liver injury in cholestatic liver diseases. Total RNA isolated using TRI Reagent (Sigma, St. Louis, MO) was purified with an RNeasy mini kit (Qiagen, Valencia, CA). Twenty micrograms cRNA was hybridized to a mouse GeneChip (U74Av2, Affymetrix, Santa Clara, CA) at the Siteman Cancer Center GeneChip facility as described by the manufacturer. Analyses used one mouse per chip. Gene expression changes were analyzed using Affymetrix MicroArray Suite 4.0 and GeneChip 3.1 Expression Analysis and Statistical Algorithms (Affymetrix). The complete methodology and full data sets for all 6 analyzed chips are available at http://bioinformatics.wustl.edu.beckerproxy.wustl.edu This study compares the injury and repair processed in wild-type mice after BDL.

Project description:BACKGROUND & AIMS: c-Jun N-terminal kinase (JNK)1 and JNK2 are expressed in hepatocytes and have overlapping and distinct functions. JNK proteins are activated, via phosphorylation, in response to acetaminophen- or CCl4-induced liver damage; the level of activation correlates with the degree of injury. SP600125, a JNK inhibitor, has been reported to block acetaminophen-induced liver injury. We investigated the role of JNK in drug-induced liver injury (DILI) in liver tissues from patients and in mice with genetic deletion of JNK in hepatocytes. METHODS: We studied liver sections from patients with DILI (due to acetaminophen, phenprocoumon, non-steroidal anti-inflammatory drugs or autoimmune hepatitis), or patients without acute liver failure (controls), collected from a DILI Biobank in Germany. Levels of total and activated (phosphorylated) JNK were measured by immunohistochemistry and western blotting. Mice with hepatocyte-specific deletion of Jnk1 (Jnk1Îhepa) or combination of Jnk1 and Jnk2 (JnkÎhepa), as well as Jnk1-floxed C57BL/6 (control) mice, were given injections of CCl4 (to induce fibrosis) or acetaminophen (to induce toxic liver injury). We performed gene expression microarray, and phosphoproteomic analyses to determine mechanisms of JNK activity in hepatocytes. RESULTS: Liver samples from DILI patients contained more activated JNK, predominantly in nuclei of hepatocytes and in immune cells, than healthy tissue. Administration of acetaminophen to JnkÎhepa mice produced a greater level of liver injury than that observed in Jnk1Îhepa or control mice, based on levels of serum markers and microscopic and histologic analysis of liver tissues. Administration of CCl4 also induced stronger hepatic injury in JnkÎhepa mice, based on increased inflammation, cell proliferation, and fibrosis progression, compared to Jnk1Îhepa or control mice. Hepatocytes from JnkÎhepa mice given acetaminophen had an increased oxidative stress response, leading to decreased activation of AMPK, total protein AMPK levels, and pJunD and subsequent necrosis. Administration of SP600125 before or with acetaminophen protected JnkÎhepa and control mice from liver injury. CONCLUSIONS: In hepatocytes, JNK1 and JNK2 appear to have combined effects in protecting mice from CCl4- and acetaminophen-induced liver injury. It is important to study the tissue-specific functions of both proteins, rather than just JNK1, in the onset of toxic liver injury. JNK inhibition with SP600125 shows off-target effects. Livers and primary hepatocytes were isolated from wild type and JNKÎhepa (Jnk1Îhepa/global Jnk2-/-) double-knockout mice and subjected to gene expression profiling.

Project description:Background: HGF/c-Met signaling plays a pivotal role in hepatocyte survival and tissue remodeling during liver regeneration. Treatment with HGF has been shown to accelerate resolution of fibrotic liver lesions in experimental animal models. To formally address the importance of c-Met signaling in hepatocytes in the context of chronic liver injury, we have used hepatocyte-specific Metfl/fl;Alb-Cre+/- conditional knockout mice (KO) and a model of liver fibrosis. Methods: CCl4 was administrated biweekly over a period of 4 weeks (injury phase), and the animals were followed over the next 4 weeks (healing phase). Macroscopic and microscopic changes during the injury and healing phases were monitored by IHC. Deposition of ECM was assessed by Sirius red staining and hydroxiproline content. Activation of hepatic stellate cells (HSC) was estimated by a-SMA using WB and IHC. Expression levels of the selected key fibrotic molecules were evaluated by RT-qPCR and WB. Time-dependent global transcriptomic changes from whole livers and isolated hepatocytes were examined using gene expression microarrays. Results: Loss of HGF/c-Met signaling in hepatocytes altered the hepatic microenvironment and dramatically aggravated hepatic fibrogenesis. Increased liver damage was associated with decreased hepatocyte proliferation, progressive accumulation of HSCs, and delayed fibrinolysis causing increased collagen deposit. Dystrophic calcification of necrotic areas impaired phagocytosis, resulting in sustained inflammatory and fibrogenic signaling further augmenting severity of fibrogenesis. Global gene-expression analysis demonstrated upregulation of key fibrogenic molecules, such as Tgf-Ã¢ and Pdgf-Ã¢, paralleled by a decreased expression of genes important for cell cycle, stress response and regeneration, which could be attributed to the c-Met deficiency in hepatocytes. Additionally, key chemotactic and inflammatory cytokines, including Ccl2, SDF1/Cxcr4 and Spp1, were upregulated in Metfl/fl;Alb-Cre+/- hepatocytes. However, the major pro-fibrotic signaling originated from the non-parenchymal cell compartments, as revealed by cell type-specific gene expression signatures. Conclusion: These results indicate that lack of c-Met signaling in hepatocytes disrupts the balance between extracellular matrix production and degradation and establish a protective role for c-Met against adverse microenvironment leading to the development of fibrotic liver disease. In the present study, we reported a detailed and comprehensive dynamic characterization of the cellular and molecular alterations involved in fibrosis in the liver of c-Met transgenic mice. Liver samples from female animals were collected at various time-points after fibrosis induction using CCL4 ranging from 0 weeks to 3 weeks. Tissue samples were divided into two parts; one was fixed in 10% formalin for histological evaluation and the other was used for RNA analysis.

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C-Met confers protection against chronic liver tissue damage and fibrosis progression after bile-duct-ligation in mice

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