Maresin 1 activates brown adipose tissue and promotes browning of white adipose tissue in mice.

OBJECTIVE: Maresin 1 (MaR1) is a docosahexaenoic acid-derived proresolving lipid mediator with insulin-sensitizing and anti-steatosis properties. Here, we aim to unravel MaR1 actions on brown adipose tissue (BAT) activation and white adipose tissue (WAT) browning. METHODS: MaR1 actions were tested in cultured murine brown adipocytes and in human mesenchymal stem cells (hMSC)-derived adipocytes. In vivo effects of MaR1 were tested in diet-induced obese (DIO) mice and lean WT and Il6 knockout (Il6-/-) mice. RESULTS: In cultured differentiated murine brown adipocytes, MaR1 reduces the expression of inflammatory genes, while stimulates glucose uptake, fatty acid utilization and oxygen consumption rate, along with the upregulation of mitochondrial mass and genes involved in mitochondrial biogenesis and function and the thermogenic program. In Leucine Rich Repeat Containing G Protein-Coupled Receptor 6 (LGR6)-depleted brown adipocytes using siRNA, the stimulatory effect of MaR1 on thermogenic genes was abrogated. In DIO mice, MaR1 promotes BAT remodeling, characterized by higher expression of genes encoding for master regulators of mitochondrial biogenesis and function and iBAT thermogenic activation, together with increased M2 macrophage markers. In addition, MaR1-treated DIO mice exhibit a better response to cold-induced BAT activation. Moreover, MaR1 induces a beige adipocyte signature in inguinal WAT of DIO mice and in hMSC-derived adipocytes. MaR1 potentiates Il6 expression in brown adipocytes and BAT of cold exposed lean WT mice. Interestingly, the thermogenic properties of MaR1 were abrogated in Il6-/- mice. CONCLUSIONS: These data reveal MaR1 as a novel agent that promotes BAT activation and WAT browning by regulating thermogenic program in adipocytes and M2 polarization of macrophages. Moreover, our data suggest that LGR6 receptor is mediating MaR1 actions on brown adipocytes, and that IL-6 is required for the thermogenic effects of MaR1.

Splicing events in the control of genome integrity: role of SLU7 and truncated SRSF3 proteins.

Genome instability is related to disease development and carcinogenesis. DNA lesions are caused by genotoxic compounds but also by the dysregulation of fundamental processes like transcription, DNA replication and mitosis. Recent evidence indicates that impaired expression of RNA-binding proteins results in mitotic aberrations and the formation of transcription-associated RNA-DNA hybrids (R-loops), events strongly associated with DNA injury. We identify the splicing regulator SLU7 as a key mediator of genome stability. SLU7 knockdown results in R-loops formation, DNA damage, cell-cycle arrest and severe mitotic derangements with loss of sister chromatid cohesion (SCC). We define a molecular pathway through which SLU7 keeps in check the generation of truncated forms of the splicing factor SRSF3 (SRp20) (SRSF3-TR). Behaving as dominant negative, or by gain-of-function, SRSF3-TR impair the correct splicing and expression of the splicing regulator SRSF1 (ASF/SF2) and the crucial SCC protein sororin. This unique function of SLU7 was found in cancer cells of different tissue origin and also in the normal mouse liver, demonstrating a conserved and fundamental role of SLU7 in the preservation of genome integrity. Therefore, the dowregulation of SLU7 and the alterations of this pathway that we observe in the cirrhotic liver could be involved in the process of hepatocarcinogenesis.

Dual Targeting of Histone Methyltransferase G9a and DNA-Methyltransferase 1 for the Treatment of Experimental Hepatocellular Carcinoma.

Epigenetic modifications such as DNA and histone methylation functionally cooperate in fostering tumor growth, including that of hepatocellular carcinoma (HCC). Pharmacological targeting of these mechanisms may open new therapeutic avenues. We aimed to determine the therapeutic efficacy and potential mechanism of action of our dual G9a histone-methyltransferase and DNA-methyltransferase 1 (DNMT1) inhibitor in human HCC cells and their crosstalk with fibrogenic cells. The expression of G9a and DNMT1, along with that of their molecular adaptor ubiquitin-like with PHD and RING finger domains-1 (UHRF1), was measured in human HCCs (n = 268), peritumoral tissues (n = 154), and HCC cell lines (n = 32). We evaluated the effect of individual and combined inhibition of G9a and DNMT1 on HCC cell growth by pharmacological and genetic approaches. The activity of our lead compound, CM-272, was examined in HCC cells under normoxia and hypoxia, human hepatic stellate cells and LX2 cells, and xenograft tumors formed by HCC or combined HCC+LX2 cells. We found a significant and correlative overexpression of G9a, DNMT1, and UHRF1 in HCCs in association with poor prognosis. Independent G9a and DNMT1 pharmacological targeting synergistically inhibited HCC cell growth. CM-272 potently reduced HCC and LX2 cells proliferation and quelled tumor growth, particularly in HCC+LX2 xenografts. Mechanistically, CM-272 inhibited the metabolic adaptation of HCC cells to hypoxia and induced a differentiated phenotype in HCC and fibrogenic cells. The expression of the metabolic tumor suppressor gene fructose-1,6-bisphosphatase (FBP1), epigenetically repressed in HCC, was restored by CM-272. Conclusion: Combined targeting of G9a/DNMT1 with compounds such as CM-272 is a promising strategy for HCC treatment. Our findings also underscore the potential of differentiation therapy in HCC.

The Epidermal Growth Factor Receptor Ligand Amphiregulin Protects From Cholestatic Liver Injury and Regulates Bile Acids Synthesis.

Intrahepatic accumulation of bile acids (BAs) causes hepatocellular injury. Upon liver damage, a potent protective response is mounted to restore the organ's function. Epidermal growth factor receptor (EGFR) signaling is essential for regeneration after most types of liver damage, including cholestatic injury. However, EGFR can be activated by a family of growth factors induced during liver injury and regeneration. We evaluated the role of the EGFR ligand, amphiregulin (AREG), during cholestatic liver injury and regulation of AREG expression by BAs. First, we demonstrated increased AREG levels in livers from patients with primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). In two murine models of cholestatic liver injury, bile duct ligation (BDL) and alpha-naphthyl-isothiocyanate (ANIT) gavage, hepatic AREG expression was markedly up-regulated. Importantly, Areg-/- mice showed aggravated liver injury after BDL and ANIT administration compared to Areg+/+ mice. Recombinant AREG protected from ANIT and BDL-induced liver injury and reduced BA-triggered apoptosis in liver cells. Oral BA administration induced ileal and hepatic Areg expression, and, interestingly, cholestyramine feeding reduced postprandial Areg up-regulation in both tissues. Most interestingly, Areg-/- mice displayed high hepatic cholesterol 7 α-hydroxylase (CYP7A1) expression, reduced serum cholesterol, and high BA levels. Postprandial repression of Cyp7a1 was impaired in Areg-/- mice, and recombinant AREG down-regulated Cyp7a1 mRNA in hepatocytes. On the other hand, BAs promoted AREG gene expression and protein shedding in hepatocytes. This effect was mediated through the farnesoid X receptor (FXR), as demonstrated in Fxr-/- mice, and involved EGFR transactivation. Finally, we show that hepatic EGFR expression is indirectly induced by BA-FXR through activation of suppressor of cytokine signaling-3 (SOC3). Conclusion: AREG-EGFR signaling protects from cholestatic injury and participates in the physiological regulation of BA synthesis.

Bile acids, FGF15/19 and liver regeneration: From mechanisms to clinical applications.

The liver has an extraordinary regenerative capacity rapidly triggered upon injury or resection. This response is intrinsically adjusted in its initiation and termination, a property termed the "hepatostat". Several molecules have been involved in liver regeneration, and among them bile acids may play a central role. Intrahepatic levels of bile acids rapidly increase after resection. Through the activation of farnesoid X receptor (FXR), bile acids regulate their hepatic metabolism and also promote hepatocellular proliferation. FXR is also expressed in enterocytes, where bile acids stimulate the expression of fibroblast growth factor 15/19 (FGF15/19), which is released to the portal blood. Through the activation of FGFR4 on hepatocytes FGF15/19 regulates bile acids synthesis and finely tunes liver regeneration as part of the "hepatostat". Here we review the experimental evidences supporting the relevance of the FXR-FGF15/19-FGFR4 axis in liver regeneration and discuss potential therapeutic applications of FGF15/19 in the prevention of liver failure. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Engineered fibroblast growth factor 19 protects from acetaminophen-induced liver injury and stimulates aged liver regeneration in mice.

The liver displays a remarkable regenerative capacity triggered upon tissue injury or resection. However, liver regeneration can be overwhelmed by excessive parenchymal destruction or diminished by pre-existing conditions hampering repair. Fibroblast growth factor 19 (FGF19, rodent FGF15) is an enterokine that regulates liver bile acid and lipid metabolism, and stimulates hepatocellular protein synthesis and proliferation. FGF19/15 is also important for liver regeneration after partial hepatectomy (PH). Therefore recombinant FGF19 would be an ideal molecule to stimulate liver regeneration, but its applicability may be curtailed by its short half-life. We developed a chimaeric molecule termed Fibapo in which FGF19 is covalently coupled to apolipoprotein A-I. Fibapo retains FGF19 biological activities but has significantly increased half-life and hepatotropism. Here we evaluated the pro-regenerative activity of Fibapo in two clinically relevant models where liver regeneration may be impaired: acetaminophen (APAP) poisoning, and PH in aged mice. The only approved therapy for APAP intoxication is N-acetylcysteine (NAC) and no drugs are available to stimulate liver regeneration. We demonstrate that Fibapo reduced liver injury and boosted regeneration in APAP-intoxicated mice. Fibapo improved survival of APAP-poisoned mice when given at later time points, when NAC is ineffective. Mechanistically, Fibapo accelerated recovery of hepatic glutathione levels, potentiated cell growth-related pathways and increased functional liver mass. When Fibapo was administered to old mice prior to PH, liver regeneration was markedly increased. The exacerbated injury developing in these mice upon PH was attenuated, and the hepatic biosynthetic capacity was enhanced. Fibapo reversed metabolic and molecular alterations that impede regeneration in aged livers. It reduced liver steatosis and downregulated p21 and hepatocyte nuclear factor 4 α (Hnf4α) levels, whereas it stimulated Foxm1b gene expression. Together our findings indicate that FGF19 variants retaining the metabolic and growth-promoting effects of this enterokine may be valuable for the stimulation of liver regeneration.

Fibroblast Growth Factor 15/19 in Hepatocarcinogenesis.

BACKGROUND: Advanced hepatocellular carcinoma (HCC) is a neoplastic disease with a very bad prognosis and increasing worldwide incidence. HCCs are resistant to conventional chemotherapy and the multikinase inhibitor sorafenib is the only agent that has shown some clinical efficacy. It is therefore important to identify key molecular mechanisms driving hepatocarcinogenesis for the development of more efficacious therapies. However, HCCs are heterogeneous tumors and different molecular subclasses have been characterized. This heterogeneity may underlie the poor performance of most of the targeted therapies so far tested in HCC patients. The fibroblast growth factor 15/19 (FGF15/19), FGF receptor 4 (FGFR4) and beta-Klotho (KLB) correceptor signaling system, a key regulator of bile acids (BA) synthesis and intermediary metabolism, is emerging as an important player in hepatocarcinogenesis. Key Messages: Aberrant signaling through the FGF15/19-FGFR4 pathway participates in the neoplastic behavior of HCC cells, promotes HCC development in mice and its overexpression has been characterized in a subset of HCC tumors from patients with poorer prognosis. Pharmacological interference with FGF15/19-FGFR4 signaling inhibits experimental hepatocarcinogenesis, and specific FGFR4 inhibitors are currently being tested in selected HCC patients with tumoral FGF19-FGFR4/KLB expression. CONCLUSIONS: Interference with FGF19-FGFR4 signaling represents a novel strategy in HCC therapy. Selection of candidate patients based on tumoral FGF19-FGFR4/KLB levels as biomarkers may result in increased efficacy of FGFR4-targeted drugs. Nevertheless, attention should be paid to the potential on target toxic effects of FGFR4 inhibitors due to the key role of this signaling system in BA metabolism.

Fibroblast growth factor 15/19 (FGF15/19) protects from diet-induced hepatic steatosis: development of an FGF19-based chimeric molecule to promote fatty liver regeneration.

OBJECTIVE: Fibroblast growth factor 15/19 (FGF15/19), an enterokine that regulates synthesis of hepatic bile acids (BA), has been proposed to influence fat metabolism. Without FGF15/19, mouse liver regeneration after partial hepatectomy (PH) is severely impaired. We studied the role of FGF15/19 in response to a high fat diet (HFD) and its regulation by saturated fatty acids. We developed a fusion molecule encompassing FGF19 and apolipoprotein A-I, termed Fibapo, and evaluated its pharmacological properties in fatty liver regeneration. DESIGN: Fgf15-/- mice were fed a HFD. Liver fat and the expression of fat metabolism and endoplasmic reticulum (ER) stress-related genes were measured. Influence of palmitic acid (PA) on FGF15/19 expression was determined in mice and in human liver cell lines. In vivo half-life and biological activity of Fibapo and FGF19 were compared. Hepatoprotective and proregenerative activities of Fibapo were evaluated in obese db/db mice undergoing PH. RESULTS: Hepatosteatosis and ER stress were exacerbated in HFD-fed Fgf15-/- mice. Hepatic expression of Pparγ2 was elevated in Fgf15-/- mice, being reversed by FGF19 treatment. PA induced FGF15/19 expression in mouse ileum and human liver cells, and FGF19 protected from PA-mediated ER stress and cytotoxicity. Fibapo reduced liver BA and lipid accumulation, inhibited ER stress and showed enhanced half-life. Fibapo provided increased db/db mice survival and improved regeneration upon PH. CONCLUSIONS: FGF15/19 is essential for hepatic metabolic adaptation to dietary fat being a physiological regulator of Pparγ2 expression. Perioperative administration of Fibapo improves fatty liver regeneration.

A GAPDH-mediated trans-nitrosylation pathway is required for feedback inhibition of bile salt synthesis in rat liver.

BACKGROUND & AIMS: Bile salts inhibit their own production by inducing the nuclear receptor small heterodimer partner (SHP) (encoded by NR0B2), which contributes to repression of the gene encoding cholesterol 7α-hydroxylase (CYP7A1), a key enzyme for the control of bile salt synthesis. On the other hand, bile salts stimulate hepatic synthesis of nitric oxide. We investigated the role of nitric oxide signaling in the control of CYP7A1 expression and the involvement in this process of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which participates in intracellular propagation of nitric oxide signals. METHODS: We studied the effects of inhibitors of nitric oxide synthesis (L-NG-nitroarginine methyl ester [L-NAME]) or protein nitrosylation (via dithiothreitol) on bile salt homeostasis in male Wistar rats placed on a cholate-rich diet for 5 days and in cultured primary hepatocytes. S-nitrosylation of GAPDH was assessed using a biotin-switch assay. Interacions of SHP with other proteins and with the Cyp7a1 promoter sequence were studied using immunoprecipitation and chromatin immunoprecipitation (ChIP) assays. We reduced the GAPDH levels in H35 cells with small interfering RNAs. GAPDH nitrosylation was assessed in normal and cholestatic rat and human livers. RESULTS: Rats placed on cholate-rich diets and given L-NAME had increased intrahepatic and biliary levels of bile salts, and deficiency in repression of CYP7A1 (at the messenger RNA and protein levels) in liver tissue, despite preserved induction of SHP. In cultured hepatocytes, L-NAME or dithiothreitol blocked cholate-induced down-regulation of CYP7A1 without impairing SHP up-regulation. In hepatocytes, cholate promoted S-nitrosylation of GAPDH and its translocation to the nucleus, accompanied by S-nitrosylation of histone deacetylase 2 (HDAC2) and Sirtuin 1 (SIRT1), deacetylases that participate, respectively, in the formation of Cyp7a1 and Shp repressor complexes. Knockdown of GAPDH prevented repression of CYP7A1 by cholate, and blocking nuclear transport of nitrosylated GAPDH reduced cholate-induced nitrosylation of HDAC2 and SIRT1; this effect was accompanied by abrogation of Cyp7a1 repression. Cholate induced binding of SHP to HDAC2 and its recruitment to the Cyp7a1 promoter; these processes were inhibited by blocking nitric oxide synthesis. Levels of nitrosylated GAPDH and nitrosylated HDAC2 were increased in cholestatic human and rat livers reflecting increased concentrations of bile salts in these conditions. CONCLUSIONS: In rat liver, excess levels of bile salts activate a GAPDH-mediated transnitrosylation cascade that provides feedback inhibition of bile salt synthesis.

Insulin-like growth factor 1 enhances bile-duct proliferation and fibrosis in Abcb4(-/-) mice.

Adamant progression of chronic cholangiopathies towards cirrhosis and limited therapeutic options leave a liver transplantation the only effective treatment. Insulin-like growth factor 1 (IGF1) effectively blocks fibrosis in acute models of liver damage in mice, and a phase I clinical trial suggested an improved liver function. IGF1 targets the biliary epithelium, but its potential benefit in chronic cholangiopathies has not been studied. To investigate the possible therapeutic effect of increased IGF1 expression, we crossed Abcb4(-/-) mice (a model for chronic cholangiopathy), with transgenic animals that overexpress IGF1. The effect on disease progression was studied in the resulting IGF1-overexpressing Abcb4(-/-) mice, and compared to that of Abcb4(-/-) littermates. The specificity of this effect was further studied in an acute model of fibrosis. The overexpression of IGF1 in transgenic Abcb4(-/-) mice resulted in stimulation of fibrogenic processes - as shown by increased expression of Tgfß, and collagens 1, 3 and 4, and confirmed by Sirius red staining and hydroxyproline measurements. Excessive extracellular matrix deposition was favored by raise in Timp1 and Timp2, while a reduction of tPA expression indicated lower tissue remodeling. These effects were accompanied by an increase in expression of inflammation markers like Tnfα, and higher presence of infiltrating macrophages. Finally, increased number of Ck19-expressing cells indicated proliferation of biliary epithelium. In contrast to liver fibrosis associated with hepatocellular damage, IGF1 overexpression does not inhibit liver fibrogenesis in chronic cholangiopathy.

Zolmitriptan: a novel portal hypotensive agent which synergizes with propranolol in lowering portal pressure.

OBJECTIVE: Only a limited proportion of patients needing pharmacological control of portal hypertension are hemodynamic responders to propranolol. Here we analyzed the effects of zolmitriptan on portal pressure and its potential interaction with propranolol. METHODS: ZOLMITRIPTAN, PROPRANOLOL OR BOTH WERE TESTED IN TWO RAT MODELS OF PORTAL HYPERTENSION: common bile duct ligation (CBDL) and CCl4-induced cirrhosis. In these animals we measured different hemodynamic parameters including portal venous pressure, arterial renal flow, portal blood flow and cardiac output. We also studied the changes in superior mesenteric artery perfusion pressure and in arterial wall cAMP levels induced by zolmitriptan, propranolol or both. Moreover, we determined the effect of splanchnic sympathectomy on the response of PVP to zolmitriptan. RESULTS: In both models of portal hypertension zolmitriptan induced a dose-dependent transient descent of portal pressure accompanied by reduction of portal flow with only slight decrease in renal flow. In cirrhotic rats, splanchnic sympathectomy intensified and prolonged zolmitriptan-induced portal pressure descent. Also, propranolol caused more intense and durable portal pressure fall when combined with zolmitriptan. Mesenteric artery perfusion pressure peaked for about 1 min upon zolmitriptan administration but showed no change with propranolol. However propranolol enhanced and prolonged the elevation in mesenteric artery perfusion pressure induced by zolmitriptan. In vitro studies showed that propranolol prevented the inhibitory effects of ß2-agonists on zolmitriptan-induced vasoconstriction and the combination of propranolol and zolmitriptan significantly reduced the elevation of cAMP caused by ß2-agonists. CONCLUSION: Zolmitriptan reduces portal hypertension and non-selective beta-blockers can improve this effect. Combination therapy deserves consideration for patients with portal hypertension failing to respond to non-selective beta-blockers.

Lack of Abcc3 expression impairs bile-acid induced liver growth and delays hepatic regeneration after partial hepatectomy in mice.

BACKGROUND & AIMS: Bile acids (BA) are increasingly recognized as important modulators of liver regeneration. Increased enterohepatic BA flux has been proposed to generate specific signals that activate hepatocyte proliferation after partial hepatectomy (PH). We have investigated the role of the BA membrane transporter Mrp3 (Abcc3), which is expressed in the liver and gut, in the hepatic growth response elicited by BA and in liver regeneration after PH. METHODS: Liver growth and regeneration, and the expression of growth-related genes, were studied in Mrp3(+/+) and Mrp3(-/-) mice fed a cholic acid (CA) supplemented diet and after 2/3 PH. Activation of the BA receptor FXR was measured in mice after in vivo transduction of the liver with a FXR-Luciferase reporter plasmid. BA levels were measured in portal serum and liver tissue by high performance liquid chromatography-tandem mass spectrometry. RESULTS: Liver growth elicited by CA feeding was significantly reduced in Mrp3(-/-) mice. These animals showed reduced FXR activation in the liver after CA administration and decreased portal serum levels of BA. Liver regeneration after PH was significantly delayed in Mrp3-deficient mice. Proliferation-related gene expression and peak DNA synthesis in Mrp3(-/-) mice occurred later than in wild types, coinciding with a retarded elevation in intra-hepatic BA levels. CONCLUSIONS: Lack of Abcc3 expression markedly impairs liver growth in response to BA and after PH. Our data suggest that Mrp3 plays a non-redundant role in the regulation of BA flux during liver regeneration.

Biliary secretion of S-nitrosoglutathione is involved in the hypercholeresis induced by ursodeoxycholic acid in the normal rat.

UNLABELLED: Ursodeoxycholic acid (UDCA) induces bicarbonate-rich hypercholeresis by incompletely defined mechanisms that involve the stimulation of adenosine triphosphate (ATP) release from cholangiocytes. As nitric oxide (NO) at a low concentration can stimulate a variety of secretory processes, we investigated whether this mediator could be implicated in the choleretic response to UDCA. Our in vivo experiments with the in situ perfused rat liver model in anesthetized rats, showed that UDCA infusion increased the biliary secretion of NO derivatives, hepatic inducible NO synthase expression, and NO synthase activity in liver tissue. UDCA also stimulated NO release by isolated rat hepatocytes. In contrast to UDCA, cholic acid was a poor inducer of NO secretion, and tauroursodeoxycholic acid showed no effect on NO secretion. Upon UDCA administration, NO was found in bile as low-molecular-weight nitrosothiols, of which S-nitrosoglutathione (GSNO) was the predominant species. UDCA-stimulated biliary NO secretion was abolished by the inhibition of inducible NO synthase with N(omega)-nitro-L-arginine methyl ester in isolated perfused livers and also in rats whose livers were depleted of glutathione with buthionine sulfoximine. Moreover, the biliary secretion of NO species was significantly diminished in UDCA-infused transport mutant [ATP-binding cassette C2 (ABCC2)/multidrug resistance-associated protein 2 (Mrp2)-deficient] rats, and this finding was consistent with the involvement of the glutathione carrier ABCC2/Mrp2 in the canalicular transport of GSNO. It was particularly noteworthy that in cultured normal rat cholangiocytes, GSNO activated protein kinase B, protected against apoptosis, and enhanced UDCA-induced ATP release to the medium; this effect was blocked by phosphoinositide 3-kinase inhibition. Finally, retrograde GSNO infusion into the common bile duct increased bile flow and biliary bicarbonate secretion. CONCLUSION: UDCA induces biliary secretion of GSNO, which contributes to stimulating ductal secretion.

Oral methylthioadenosine administration attenuates fibrosis and chronic liver disease progression in Mdr2-/- mice.

BACKGROUND: Inflammation and fibrogenesis are directly related to chronic liver disease progression, including hepatocellular carcinoma (HCC) development. Currently there are few therapeutic options available to inhibit liver fibrosis. We have evaluated the hepatoprotective and anti-fibrotic potential of orally-administered 5'-methylthioadenosine (MTA) in Mdr2(-/-) mice, a clinically relevant model of sclerosing cholangitis and spontaneous biliary fibrosis, followed at later stages by HCC development. METHODOLOGY: MTA was administered daily by gavage to wild type and Mdr2(-/-) mice for three weeks. MTA anti-inflammatory and anti-fibrotic effects and potential mechanisms of action were examined in the liver of Mdr2(-/-) mice with ongoing fibrogenesis and in cultured liver fibrogenic cells (myofibroblasts). PRINCIPAL FINDINGS: MTA treatment reduced hepatomegaly and liver injury. α-Smooth muscle actin immunoreactivity and collagen deposition were also significantly decreased. Inflammatory infiltrate, the expression of the cytokines IL6 and Mcp-1, pro-fibrogenic factors like TGFß2 and tenascin-C, as well as pro-fibrogenic intracellular signalling pathways were reduced by MTA in vivo. MTA inhibited the activation and proliferation of isolated myofibroblasts and down-regulated cyclin D1 gene expression at the transcriptional level. The expression of JunD, a key transcription factor in liver fibrogenesis, was also reduced by MTA in activated myofibroblasts. CONCLUSIONS/SIGNIFICANCE: Oral MTA administration was well tolerated and proved its efficacy in reducing liver inflammation and fibrosis. MTA may have multiple molecular and cellular targets. These include the inhibition of inflammatory and pro-fibrogenic cytokines, as well as the attenuation of myofibroblast activation and proliferation. Downregulation of JunD and cyclin D1 expression in myofibroblasts may be important regarding the mechanism of action of MTA. This compound could be a good candidate to be tested for the treatment of (biliary) liver fibrosis.

The epidermal growth factor receptor ligand amphiregulin is a negative regulator of hepatic acute-phase gene expression.

BACKGROUND/AIMS: The modulation of the hepatic acute-phase reaction (APR) that occurs during inflammation and liver regeneration is important for allowing normal hepatocellular proliferation and the restoration of homeostasis. Activation of acute-phase protein (APP) gene expression by interleukin-6 (IL-6)-type cytokines is thought to be counteracted by growth factors released during hepatic inflammation and regeneration. The epidermal growth factor receptor (EGFR) ligand amphiregulin (AR) is readily induced by inflammatory signals and plays a nonredundant protective role during liver injury. In this paper, we investigated the role of AR as a modulator of liver APP gene expression. METHODS: Expression of APP genes was measured in the livers of AR(+/+) and AR(-/-)mice during inflammation and regeneration and in cultured liver cells treated with AR and oncostatin M (OSM). Crosstalk between AR and OSM signalling was studied. RESULTS: APP genes were overexpressed in the livers of AR(-/-) mice during inflammation and hepatocellular regeneration. In cultured AR-null hepatocytes and human hepatocellular carcinoma (HCC) cells after AR knockdown, APP gene expression is enhanced. AR counteracts OSM-triggered signal transducer and activator of transcription 3 signalling in hepatocytes and attenuates APP gene transcription. CONCLUSIONS: Our data support the relevance of EGFR-mediated signalling in the modulation of cytokine-activated pathways. We have identified AR as a key regulator of hepatic APP gene expression during inflammation and liver regeneration.

Enhanced actions of insulin-like growth factor-I and interferon-alpha co-administration in experimental cirrhosis.

BACKGROUND: Cirrhosis is a diffuse process of hepatic fibrosis and regenerative nodule formation. The liver is the major source of circulating insulin-like growth factor-I (IGF-I) whose plasma levels are diminished in cirrhosis. IGF-I supplementation has been shown to induce beneficial effects in cirrhosis, including antifibrogenic and hepatoprotective effects. On other hand, interferon-alpha (IFN-alpha) therapy seems to suppress the progression of hepatic fibrosis. AIMS: The aim of this study was to investigate the effect of the co-administration of IGF-I+IFN-alpha to Wistar rats with CCl(4)-induced cirrhosis, exploring liver function tests, hepatic lipid peroxidation and histopathology. METHODS: The mechanisms underlying the effects of these agents were studied by reverse transcription-polymerase chain reaction, determining the expression of some factors [hepatocyte growth factor (HGF), transforming growth factor-beta (TGF-beta), alpha-smooth muscle actin, collagen, tissular inhibitor of metalloproteinases-1 and pregnane X receptor (PXR)] involved in fibrogenesis, fibrolysis and/or hepatoprotection. RESULTS: Both IGF-I and IFN-alpha exerted significant effects on fibrogenesis. IGF-I significantly increased serum albumin and HGF whereas IFN-alpha-therapy did not. The inhibition of TGF-beta expression was only observed by the effect of IFN-alpha-therapy. In addition, only the co-administration of IGF-I and IFN-alpha was able to increase the PXR. The combined therapy with both factors improved liver function tests, hepatic lipid peroxidation and reduced fibrosis, inducing a relevant histological improvement, reducing fibrosis and recovering hepatic architecture. CONCLUSION: The co-administration IGF-I+IFN enhanced all the beneficial effects observed with each factor separately, showing an additive action on histopathology and PXR expression, which is involved in the inhibition of fibrogenesis.

Bicarbonate-rich choleresis induced by secretin in normal rat is taurocholate-dependent and involves AE2 anion exchanger.

Canalicular bile is modified along bile ducts through reabsorptive and secretory processes regulated by nerves, bile salts, and hormones such as secretin. Secretin stimulates ductular cystic fibrosis transmembrane conductance regulator (CFTR)-dependent Cl- efflux and subsequent biliary HCO3- secretion, possibly via Cl-/HCO3- anion exchange (AE). However, the contribution of secretin to bile regulation in the normal rat, the significance of choleretic bile salts in secretin effects, and the role of Cl-/HCO3- exchange in secretin-stimulated HCO3- secretion all remain unclear. Here, secretin was administered to normal rats with maintained bile acid pool via continuous taurocholate infusion. Bile flow and biliary HCO3- and Cl- excretion were monitored following intrabiliary retrograde fluxes of saline solutions with and without the Cl- channel inhibitor 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) or the Cl-/HCO3- exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). Secretin increased bile flow and biliary excretion of HCO3- and Cl-. Interestingly, secretin effects were not observed in the absence of taurocholate. Whereas secretin effects were all blocked by intrabiliary NPPB, DIDS only inhibited secretin-induced increases in bile flow and HCO3- excretion but not the increased Cl- excretion, revealing a role of biliary Cl-/HCO3- exchange in secretin-induced, bicarbonate-rich choleresis in normal rats. Finally, small hairpin RNA adenoviral constructs were used to demonstrate the involvement of the Na+-independent anion exchanger 2 (AE2) through gene silencing in normal rat cholangiocytes. AE2 gene silencing caused a marked inhibition of unstimulated and secretin-stimulated Cl-/HCO3- exchange. In conclusion, maintenance of the bile acid pool is crucial for secretin to induce bicarbonate-rich choleresis in the normal rat and that this occurs via a chloride-bicarbonate exchange process consistent with AE2 function.

Altered liver gene expression in CCl4-cirrhotic rats is partially normalized by insulin-like growth factor-I.

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.