http://hdl.handle.net/10171/3484 Wed, 19 Jun 2013 15:45:40 GMT 2013-06-19T15:45:40Z http://hdl.handle.net/10171/27496 Title: New therapies for hepatocellular carcinoma Author(s) : Avila, M.A. (Matías Antonio); Berasain, C. (Carmen); Sangro, B. (Bruno); Prieto, J. (Jesús) Abstract: Hepatocellular carcinoma (HCC), one of the most common cancers worldwide, is often diagnosed at an advanced stage when most potentially curative therapies such as resection, transplantation or percutaneous and transarterial interventions are of limited efficacy. The fact that HCC is resistant to conventional chemotherapy, and is rarely amenable to radiotherapy, leaves this disease with no effective therapeutic options and a very poor prognosis. Therefore, the development of more effective therapeutic tools and strategies is much needed. HCCs are phenotypically and genetically heterogeneous tumors that commonly emerge on a background of chronic liver disease. However, in spite of this heterogeneity recent insights into the biology of HCC suggest that certain signaling pathways and molecular alterations are likely to play essential roles in HCC development by promoting cell growth and survival. The identification of such mechanisms may open new avenues for the prevention and treatment of HCC through the development of targeted therapies. In this review we will describe the new potential therapeutic targets and clinical developments that have emerged from progress in the knowledge of HCC biology, In addition, recent advances in gene therapy and combined cell and gene therapy, together with new radiotherapy techniques and immunotherapy in patients with HCC will be discussed. Sat, 31 Dec 2005 23:00:00 GMT http://hdl.handle.net/10171/27496 2005-12-31T23:00:00Z http://hdl.handle.net/10171/27495 Title: S-adenosylmethionine and methylthioadenosine are antiapoptotic in cultured rat hepatocytes but proapoptotic in human hepatoma cells Author(s) : Ansorena, E. (Eduardo); Garcia-Trevijano, E.R. (Elena R.); Martinez-Chantar, M.L. (María L.); Huang, Z.Z. (Zong-Zhi); Chen, L. (Lixin); Mato, J.M. (José M.); Iraburu, M. (María); Lu, S.C. (Shelly C.); Avila, M.A. (Matías A.) Abstract: S-adenosylmethionine (AdoMet) is an essential compound in cellular transmethylation reactions and a precursor of polyamine and glutathione synthesis in the liver. In liver injury, the synthesis of AdoMet is impaired and its availability limited. AdoMet administration attenuates experimental liver damage, improves survival of alcoholic patients with cirrhosis, and prevents experimental hepatocarcinogenesis. Apoptosis contributes to different liver injuries, many of which are protected by AdoMet. The mechanism of AdoMet's hepatoprotective and chemopreventive effects are largely unknown. The effect of AdoMet on okadaic acid (OA)-induced apoptosis was evaluated using primary cultures of rat hepatocytes and human hepatoma cell lines. AdoMet protected rat hepatocytes from OA-induced apoptosis dose dependently. It attenuated mitochondrial cytochrome c release, caspase 3 activation, and poly(ADP-ribose) polymerase cleavage. These effects were independent from AdoMet-dependent glutathione synthesis, and mimicked by 5'-methylthioadenosine (MTA), which is derived from AdoMet. Interestingly, AdoMet and MTA did not protect HuH7 cells from OA-induced apoptosis; conversely both compounds behaved as proapoptotic agents. AdoMet's proapoptotic effect was dose dependent and observed also in HepG2 cells. In conclusion, AdoMet exerts opposing effects on apoptosis in normal versus transformed hepatocytes that could be mediated through its conversion to MTA. These effects may participate in the hepatoprotective and chemopreventive properties of this safe and well-tolerated drug. Mon, 31 Dec 2001 23:00:00 GMT http://hdl.handle.net/10171/27495 2001-12-31T23:00:00Z http://hdl.handle.net/10171/27494 Title: Methylthioadenosine (MTA) inhibits melanoma cell proliferation and in vivo tumor growth Author(s) : Andreu-Perez, P. (Pedro); Hernandez-Losa, J. (Javier); Moline, T. (Teresa); Gil, R. (Rosa); Grueso, J. (Judit); Pujol, A. (Anna); Cortes, J. (Javier); Avila, M.A. (Matías Antonio); Recio, J.A. (Juan A.) Abstract: BACKGROUND: Melanoma is the most deadly form of skin cancer without effective treatment. Methylthioadenosine (MTA) is a naturally occurring nucleoside with differential effects on normal and transformed cells. MTA has been widely demonstrated to promote anti-proliferative and pro-apoptotic responses in different cell types. In this study we have assessed the therapeutic potential of MTA in melanoma treatment. METHODS: To investigate the therapeutic potential of MTA we performed in vitro proliferation and viability assays using six different mouse and human melanoma cell lines wild type for RAS and BRAF or harboring different mutations in RAS pathway. We also have tested its therapeutic capabilities in vivo in a xenograft mouse melanoma model and using variety of molecular techniques and tissue culture we investigated its anti-proliferative and pro-apoptotic properties. RESULTS: In vitro experiments showed that MTA treatment inhibited melanoma cell proliferation and viability in a dose dependent manner, where BRAF mutant melanoma cell lines appear to be more sensitive. Importantly, MTA was effective inhibiting in vivo tumor growth. The molecular analysis of tumor samples and in vitro experiments indicated that MTA induces cytostatic rather than pro-apoptotic effects inhibiting the phosphorylation of Akt and S6 ribosomal protein and inducing the down-regulation of cyclin D1. CONCLUSIONS: MTA inhibits melanoma cell proliferation and in vivo tumor growth particularly in BRAF mutant melanoma cells. These data reveal a naturally occurring drug potentially useful for melanoma treatment. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/10171/27494 2009-12-31T23:00:00Z http://hdl.handle.net/10171/23279 Title: Transformed but not normal hepatocytes express UCP2 Author(s) : Carretero, M.V. (M. Victoria); Torres, L. (Luis); Latasa, M.U. (María Ujué); Garcia-Trevijano, E.R. (Elena R.); Prieto, J. (Jesús); Mato, J.M. (José María); Avila, M.A. (Matías Antonio) Abstract: Uncoupling protein 2 (UCP2) expression in liver is restricted to non-parenchymal cells. By means of differential display screening between normal rat liver and H4IIE hepatoma cells we have isolated a cDNA clone encompassing part of UCP2 cDNA. Northern blot analysis revealed that UCP2 is expressed in some hepatocarcinoma cell lines, while it is absent in adult hepatocytes. UCP2 mRNA in H4IIE cells was downregulated when cells were cultured for 36 h in 0.1% serum and its expression was restored upon addition of 10% serum or phorbol esters. Hypomethylation of UCP2 was observed in transformed UCP2 expressing cells. Our results indicate that UCP2 is expressed in some hepatocarcinoma cell lines and that serum components may participate in maintaining elevated UCP2 levels. Wed, 31 Dec 1997 23:00:00 GMT http://hdl.handle.net/10171/23279 1997-12-31T23:00:00Z http://hdl.handle.net/10171/23278 Title: L-methionine availability regulates expression of the methionine adenosyltransferase 2A gene in human hepatocarcinoma cells: role of S-adenosylmethionine Author(s) : Martinez-Chantar, M.L. (María Luz); Latasa, M.U. (María Ujué); Varela-Rey, M. (Marta); Lu, S.C. (Shelly C.); Garcia-Trevijano, E.R. (Elena R.); Mato, J.M. (José María); Avila, M.A. (Matías Antonio) Abstract: In mammals, methionine adenosyltransferase (MAT), the enzyme responsible for S-adenosylmethionine (AdoMet) synthesis, is encoded by two genes, MAT1A and MAT2A. In liver, MAT1A expression is associated with high AdoMet levels and a differentiated phenotype, whereas MAT2A expression is associated with lower AdoMet levels and a dedifferentiated phenotype. In the current study, we examined regulation of MAT2A gene expression by l-methionine availability using HepG2 cells. In l-methionine-deficient cells, MAT2A gene expression is rapidly induced, and methionine adenosyltransferase activity is increased. Restoration of l-methionine rapidly down-regulates MAT2A mRNA levels; for this effect, l-methionine needs to be converted into AdoMet. This novel action of AdoMet is not mediated through a methyl transfer reaction. MAT2A gene expression was also regulated by 5'-methylthioadenosine, but this was dependent on 5'-methylthioadenosine conversion to methionine through the salvage pathway. The transcription rate of the MAT2A gene remained unchanged during l-methionine starvation; however, its mRNA half-life was significantly increased (from 100 min to more than 3 h). The effect of l-methionine withdrawal on MAT2A mRNA stabilization requires both gene transcription and protein synthesis. We conclude that MAT2A gene expression is modulated as an adaptive response of the cell to l-methionine availability through its conversion to AdoMet. Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/10171/23278 2002-12-31T23:00:00Z http://hdl.handle.net/10171/23277 Title: Methionine adenosyltransferase II beta subunit gene expression provides a proliferative advantage in human hepatoma Author(s) : Martinez-Chantar, M.L. (María Luz); Garcia-Trevijano, E.R. (Elena R.); Latasa, M.U. (María Ujué); Martin-Duce, A. (Antonio); Fortes, P. (Puri); Caballeria, J. (Juan); Avila, M.A. (Matías Antonio); Mato, J.M. (José María) Abstract: BACKGROUND & AIMS: Of the 2 genes (MAT1A, MAT2A) encoding methionine adenosyltransferase, the enzyme that synthesizes S-adenosylmethionine, MAT1A, is expressed in liver, whereas MAT2A is expressed in extrahepatic tissues. In liver, MAT2A expression associates with growth, dedifferentiation, and cancer. Here, we identified the beta subunit as a regulator of proliferation in human hepatoma cell lines. The beta subunit has been cloned and shown to lower the K(m) of methionine adenosyltransferase II alpha2 (the MAT2A product) for methionine and to render the enzyme more susceptible to S-adenosylmethionine inhibition. METHODS: Methionine adenosyltransferase II alpha2 and beta subunit expression was analyzed in human and rat liver and hepatoma cell lines and their interaction studied in HuH7 cells. beta Subunit expression was up- and down-regulated in human hepatoma cell lines and the effect on DNA synthesis determined. RESULTS: We found that beta subunit is expressed in rat extrahepatic tissues but not in normal liver. In human liver, beta subunit expression associates with cirrhosis and hepatoma. beta Subunit is expressed in most (HepG2, PLC, and Hep3B) but not all (HuH7) hepatoma cell lines. Transfection of beta subunit reduced S-adenosylmethionine content and stimulated DNA synthesis in HuH7 cells, whereas down-regulation of beta subunit expression diminished DNA synthesis in HepG2. The interaction between methionine adenosyltransferase II alpha2 and beta subunit was demonstrated in HuH7 cells. CONCLUSIONS: Our findings indicate that beta subunit associates with cirrhosis and cancer providing a proliferative advantage in hepatoma cells through its interaction with methionine adenosyltransferase II alpha2 and down-regulation of S-adenosylmethionine levels. Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/10171/23277 2002-12-31T23:00:00Z http://hdl.handle.net/10171/23276 Title: The response of the hepatocyte to ischemia Author(s) : Massip-Salcedo, M. (M.); Rosello-Catafau, J. (J.); Prieto, J. (Jesús); Avila, M.A. (Matías Antonio); Peralta, C. (C.) Abstract: BACKGROUND: Ischemia-reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, in spite of several attempts to solve the problem. AIMS: To evaluate the response of the hepatocyte to ischemia METHODS: Published data are thus revised. RESULTS: The response of the hepatocyte to ischemia is based on the sensitivity of hepatocytes to different types of ischemia, the kind of cell death of the hepatocyte when it is subjected to ischemia, and on the response of the hepatocyte to the different times and extents of ischemia. Clinical factors including starvation, graft, age, and hepatic steatosis, all of which contribute to enhancing liver susceptibility to ischemia/reperfusion injury. CONCLUSION: Ischemic preconditioning, based on the induction of a brief ischemia to the liver prior to a prolonged ischemia, has been applied in tumor hepatic resections for reducing hepatic I/R injury and recent clinical studies suggest that this surgical strategy could be appropriate for liver transplantation. Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/10171/23276 2006-12-31T23:00:00Z http://hdl.handle.net/10171/23275 Title: NO sensitizes rat hepatocytes to proliferation by modifying S-adenosylmethionine levels Author(s) : Garcia-Trevijano, E.R. (Elena R.); Martinez-Chantar, M.L. (María Luz); Latasa, M.U. (María Ujué); Mato, J.M. (José María); Avila, M.A. (Matías Antonio) Abstract: BACKGROUND & AIMS: Liver regeneration is a fundamental response of this organ to injury. Hepatocyte proliferation is triggered by growth factors, such as hepatocyte growth factor. However, hepatocytes need to be primed to react to mitogenic signals. It is known that nitrous oxide (NO), generated after partial hepatectomy, plays an important role in hepatocyte growth. Nevertheless, the molecular mechanisms behind this priming event are not completely known. S-adenosylmethionine (AdoMet) synthesis by methionine adenosyltransferase is the first step in methionine metabolism, and NO regulates hepatocyte S-adenosylmethionine levels through specific inhibition of this enzyme. We have studied the modulation of hepatocyte growth factor-induced proliferation by NO through the regulation of S-adenosylmethionine levels. METHODS: Studies were conducted in cultured rat hepatocytes isolated by collagenase perfusion, which triggers NO synthesis. RESULTS: The mitogenic response to hepatocyte growth factor was blunted when inducible NO synthase was inhibited; this process was overcome by the addition of an NO donor. This effect was dependent on methionine concentration in culture medium and intracellular S-adenosylmethionine levels. Accordingly, we found that S-adenosylmethionine inhibits hepatocyte growth factor-induced cyclin D1 and D2 expression, activator protein 1 induction, and hepatocyte proliferation. CONCLUSIONS: Together our findings indicate that NO may switch hepatocytes into a hepatocyte growth factor-responsive state through the down-regulation of S-adenosylmethionine levels. Mon, 31 Dec 2001 23:00:00 GMT http://hdl.handle.net/10171/23275 2001-12-31T23:00:00Z http://hdl.handle.net/10171/23268 Title: Altered liver gene expression in CCl4-cirrhotic rats is partially normalized by insulin-like growth factor-I Author(s) : Mirpuri, E. (Eduardo); Garcia-Trevijano, E.R. (Elena R.); Castilla-Cortazar, I. (Inma); Berasain, C. (Carmen); Quiroga, J. (Jorge); Rodriguez-Ortigosa, C.M. (Carlos M.); Mato, J.M. (José María); Prieto, J. (Jesús); Avila, M.A. (Matías Antonio) Abstract: We have previously shown that the administration of low doses of insulin-like growth factor-I (IGF-I) to CCl4-cirrhotic rats improves liver function and reduces fibrosis. To better understand the mechanisms behind the hepatoprotective effects of IGF-I, and to identify those genes whose expression is affected in cirrhosis and after IGF-1 treatment, we have performed differential display of mRNA analysis by means of polymerase chain reaction (PCR) in livers from control and CCl4-cirrhotic rats treated or not with IGF-I. We have identified 16 genes that were up- or down-regulated in the cirrhotic liver. IGF-I treatment partially normalized the expression of eight of these genes, including serine proteinase inhibitors such as serpin-2 and alpha-1-antichymotripsin, alpha-1-acid glycoprotein, and alpha-2u-globulin. Additionally, we show that IGF-I enhanced the regenerative activity in the cirrhotic liver, as determined by the increased expression of the proliferating cell nuclear antigen (PCNA). Finally, IGF-I treatment partially restored the expression of growth hormone receptor (GHR) and the levels of global genomic DNA methylation, which are reduced in human and experimental cirrhosis. Taken together, our observations confirm the hepatoprotective effects of IGF-I, and suggest that this action can be exerted in part through the normalization of liver gene expression, growth hormone (GH) responsiveness and global genomic DNA methylation. Mon, 31 Dec 2001 23:00:00 GMT http://hdl.handle.net/10171/23268 2001-12-31T23:00:00Z http://hdl.handle.net/10171/23261 Title: Amphiregulin contributes to the transformed phenotype of human hepatocellular carcinoma cells Author(s) : Castillo, J. (Josefa); Erroba, E. (Elena); Perugorria, M.J. (María J.); Santamaria, M. (Mónica); Lee, D.C. (David C.); Prieto, J. (Jesús); Avila, M.A. (Matías Antonio); Berasain, C. (Carmen) Abstract: Hepatocellular carcinoma is a major cause of cancer-related deaths. Current treatments are not effective, and the identification of relevant pathways and novel therapeutic targets are much needed. Increasing evidences point to the activation of the epidermal growth factor receptor (EGFR) as an important mechanism in the development of hepatocarcinoma. We previously described that amphiregulin (AR), a ligand of the EGFR, is not expressed in healthy liver but is up-regulated during chronic liver injury, the background on which most liver tumors develop. Now, we have studied the expression and role of AR in human hepatocarcinoma. AR expression and function was studied in human liver tumors and cell lines. AR is expressed in human hepatocellular carcinoma tissues and cell lines and behaves as a mitogenic and antiapoptotic growth factor for hepatocarcinoma cells. We provide several lines of evidence, including AR silencing by small interfering RNAs and inhibition of amphiregulin by neutralizing antibodies, showing the existence of an AR-mediated autocrine loop that contributes to the transformed phenotype. Indeed, interference with endogenous AR production resulted in reduced constitutive EGFR signaling, inhibition of cell proliferation, anchorage-independent growth, and enhanced apoptosis. Moreover, knockdown of AR potentiated transforming growth factor-beta and doxorubicin-induced apoptosis. Conversely, overexpression of AR in SK-Hep1 cells enhanced their proliferation rate, anchorage-independent growth, drug resistance, and in vivo tumorigenic potential. These observations suggest that AR is involved in the acquisition of neoplastic traits in the liver and thus constitutes a novel therapeutic target in human hepatocarcinoma. Sat, 31 Dec 2005 23:00:00 GMT http://hdl.handle.net/10171/23261 2005-12-31T23:00:00Z http://hdl.handle.net/10171/23259 Title: Up-regulation of the anti-inflammatory adipokine adiponectin in acute liver failure in mice Author(s) : Wolf, A.M. (Anna María); Wolf, D. (Dominik); Avila, M.A. (Matías Antonio); Moschen, A.R. (Alexander R.); Berasain, C. (Carmen); Enrich, B. (Barbara); Rumpold, H. (Holger); Tilg, H. (Herbert) Abstract: BACKGROUND/AIMS: Recent reports suggest that the adipose tissue and adipokines are potent modulators of inflammation. However, there is only scarce knowledge on the functional role and regulation of endogenous adiponectin in non-fat tissues such as the liver under conditions of acute inflammation. METHODS: In the present study, we investigated adiponectin expression in healthy murine liver tissue and under inflammatory conditions in vivo. RESULTS: Adiponectin mRNA was readily detectable in healthy liver tissue and further increased in ConA-mediated acute liver failure. Adiponectin protein expression was mainly found in hepatic endothelial cells. In vitro adiponectin mRNA expression was detectable in several cell types, including primary hepatic sinusoidal endothelial cells, stellate cells, and macrophages. Mice pretreated with adiponectin before ConA administration developed reduced hepatic injury as shown by decreased release of transaminases and reduced hepatocellular apoptotis. Of note, TNF-alpha levels were not affected by adiponectin, whereas IL-10 production was increased. Neutralisation of IL-10 diminished the protective effect of adiponectin. CONCLUSIONS: Adiponectin expression is up-regulated in ConA-mediated acute liver failure. Therefore, adiponectin might play a role in the control and limitation of inflammation in the liver. Moreover, our data suggest a role for IL-10 in adiponectin-mediated hepatoprotection. Sat, 31 Dec 2005 23:00:00 GMT http://hdl.handle.net/10171/23259 2005-12-31T23:00:00Z http://hdl.handle.net/10171/23256 Title: Identification of argininosuccinate lyase as a hypoxia-responsive gene in rat hepatocytes Author(s) : Latasa, M.U. (María Ujué); Carretero, M.V. (M. Victoria); Garcia-Trevijano, E.R. (Elena R.); Torres, L. (Luis); Mato, J.M. (José María); Avila, M.A. (Matías Antonio) Abstract: BACKGROUND/AIMS: The differential oxygenation of periportal and perivenous hepatocytes has been demonstrated as a major determinant in the zonated expression of certain metabolic pathways in the liver. We have searched for novel genes whose expression could be modulated by hypoxia in cultured rat hepatocytes. METHODS: Primary cultures of rat hepatocytes were incubated under normoxic (21% oxygen) or hypoxic (3% oxygen) conditions for 6 h. Differences in gene expression under both conditions were analyzed using the technique of differential display by means of PCR. RESULTS: We have identified the enzyme argininosuccinate lyase (ASL) as being downregulated by hypoxia. ASL is a cytosolic protein which participates in urea metabolism. ASL expression was time-dependently reduced in hypoxia. Hypoxia modulated the responses of this gene to the two main hormonal signals which induce ASL mRNA: glucocorticoids and cAMP. ASL mRNA levels decreased in response to ATP-reducing agents. CoCl2 mimicked the effect of hypoxia, suggesting the implication of a hemoprotein in this response. Hypoxia did not affect ASL mRNA stability, indicating that this effect occurs at the transcriptional level. CONCLUSIONS: Our observations suggest that differences in oxygen levels across the hepatic parenchyma could participate in the zonated expression of ASL. Fri, 31 Dec 1999 23:00:00 GMT http://hdl.handle.net/10171/23256 1999-12-31T23:00:00Z http://hdl.handle.net/10171/23255 Title: Novel role for amphiregulin in protection from liver injury Author(s) : Berasain, C. (Carmen); Garcia-Trevijano, E.R. (Elena R.); Castillo, J. (Josefa); Erroba, E. (Elena); Santamaria, M. (Mónica); Lee, D.C. (David C.); Prieto, J. (Jesús); Avila, M.A. (Matías Antonio) Abstract: Clinically, the Fas and Fas ligand system plays a central role in the development of hepatocyte apoptosis, a process contributing to a broad spectrum of liver diseases. Therefore, the development of therapies aimed at the inhibition of hepatocyte apoptosis is a major issue. Activation of the epidermal growth factor receptor has been shown to convey survival signals to the hepatocyte. To learn about the endogenous response of epidermal growth factor receptor ligands during Fas-mediated liver injury we investigated the expression of epidermal growth factor, transforming growth factor alpha, heparin-binding epidermal growth factor-like growth factor, betacellulin, epiregulin, and amphiregulin in the liver of mice challenged with Fas-agonist antibody. Amphiregulin expression, barely detectable in healthy liver, was significantly up-regulated. Amphiregulin administration abrogated Fas-mediated liver injury in mice and showed direct anti-apoptotic effects in primary hepatocytes. Amphiregulin activated the Akt and signal transducer and activator of transcription-3 survival pathways, and up-regulated Bcl-xL expression. Amphiregulin knock-out mice showed signs of chronic liver damage in the absence of any noxious treatment, and died faster than wild type mice in response to lethal doses of Fas-agonist antibody. In contrast, these mice were more resistant against sublethal liver damage, supporting the hypothesis that chronic liver injury can precondition hepatocytes inducing resistance to subsequent cell death. These results show that amphiregulin is a protective factor induced in response to liver damage and that it may be therapeutic in liver diseases. Fri, 31 Dec 2004 23:00:00 GMT http://hdl.handle.net/10171/23255 2004-12-31T23:00:00Z http://hdl.handle.net/10171/23254 Title: Amphiregulin: an early trigger of liver regeneration in mice Author(s) : Berasain, C. (Carmen); Garcia-Trevijano, E.R. (Elena R.); Castillo, J. (Josefa); Erroba, E. (Elena); Lee, D.C. (David C.); Prieto, J. (Jesús); Avila, M.A. (Matías Antonio) Abstract: BACKGROUND AND AIMS: Liver regeneration is a unique response directed to restore liver mass after resection or injury. The survival and proliferative signals triggered during this process are conveyed by a complex network of cytokines and growth factors acting in an orderly manner. Activation of the epidermal growth factor receptor is thought to play an important role in liver regeneration. Amphiregulin is a member of the epidermal growth factor family whose expression is not detectable in healthy liver. We have investigated the expression of amphiregulin in liver injury and its role during liver regeneration after partial hepatectomy. METHODS: Amphiregulin gene expression was examined in healthy and cirrhotic human and rat liver, in rodent liver regeneration after partial hepatectomy, and in primary hepatocytes. The proliferative effects and intracellular signaling of amphiregulin were studied in isolated hepatocytes. The in vivo role of amphiregulin in liver regeneration after partial hepatectomy was analyzed in amphiregulin-null mice. RESULTS: Amphiregulin gene expression is detected in chronically injured human and rat liver and is rapidly induced after partial hepatectomy in rodents. Amphiregulin expression is induced in isolated hepatocytes by interleukin 1beta and prostaglandin E(2), but not by hepatocyte growth factor, interleukin 6, or tumor necrosis factor alpha. We show that amphiregulin behaves as a primary mitogen for isolated hepatocytes, acting through the epidermal growth factor receptor. Finally, amphiregulin-null mice display impaired proliferative responses after partial liver resection. CONCLUSIONS: Our findings indicate that amphiregulin is an early-response growth factor that may contribute to the initial phases of liver regeneration. Fri, 31 Dec 2004 23:00:00 GMT http://hdl.handle.net/10171/23254 2004-12-31T23:00:00Z http://hdl.handle.net/10171/23253 Title: Induction of TIMP-1 expression in rat hepatic stellate cells and hepatocytes: a new role for homocysteine in liver fibrosis Author(s) : Torres, L. (Luis); Garcia-Trevijano, E.R. (Elena R.); Rodriguez, J.A. (José A.); Carretero, M.V. (M. Victoria); Bustos, M. (Matilde); Fernandez, E. (Estefanía); Eguinoa, E. (Ezequiel); Mato, J.M. (José María); Avila, M.A. (Matías Antonio) Abstract: Elevated plasma levels of homocysteine have been shown to interfere with normal cell function in a variety of tissues and organs, such as the vascular wall and the liver. However, the molecular mechanisms behind homocysteine effects are not completely understood. In order to better characterize the cellular effects of homocysteine, we have searched for changes in gene expression induced by this amino acid. Our results show that homocysteine is able to induce the expression and synthesis of the tissue inhibitor of metalloproteinases-1 (TIMP-1) in a variety of cell types ranging from vascular smooth muscle cells to hepatocytes, HepG2 cells and hepatic stellate cells. In this latter cell type, homocysteine also stimulated alpha 1(I) procollagen mRNA expression. TIMP-1 induction by homocysteine appears to be mediated by its thiol group. Additionally, we demonstrate that homocysteine is able to promote activating protein-1 (AP-1) binding activity, which has been shown to be critical for TIMP-1 induction. Our findings suggest that homocysteine may alter extracellular matrix homeostasis on diverse tissular backgrounds besides the vascular wall. The liver could be considered as another target for such action of homocysteine. Consequently, the elevated plasma levels of this amino acid found in different pathological or nutritional circumstances may cooperate with other agents, such as ethanol, in the onset of liver fibrosis. Thu, 31 Dec 1998 23:00:00 GMT http://hdl.handle.net/10171/23253 1998-12-31T23:00:00Z