Leptin is essential for the hepatic fibrogenic response to chronic liver injury

BACKGROUND/AIMS: Obesity is associated with hyperleptinemia and is also a risk factor for fibrosis and severity of fibrosis in several chronic liver diseases. The correlation between increased leptin, obesity and hepatic fibrosis prompted us to hypothesise that leptin has profibrogenic effects on the liver.METHODS: We analysed the role of leptin in liver fibrosis in leptin-deficient mice fed a diet which generates steatohepatitis, and in chronic carbon tetrachloride-induced hepatic injury.RESULTS: Leptin-deficient mice failed to develop fibrosis during steatohepatitis or in response to chronic toxic liver injury, and failed to up-regulate collagen-I while developing similar hepatic injury as their genetic controls. Restitution of physiological levels of circulating leptin by injection of exogenous leptin, but not correction of the obese phenotype by dietary manipulation, restored liver fibrosis in leptin-deficient mice during chronic liver injury. These results confirmed the absolute requirement of leptin for hepatic fibrosis. We showed that leptin deficiency did not alter hepatic TNF regulation but that leptin is necessary for induction of bioactive transforming growth factor beta 1 (TGFbeta1) protein in the context of chronic liver injury.CONCLUSIONS: These data establish that leptin is an essential mediator of hepatic fibrosis in response to chronic liver injury, whether metabolic or toxic in aetiology.     

Attenuated liver progenitor (oval) cell and fibrogenic responses to the choline deficient, ethionine supplemented diet in the BALB/c inbred strain of mice

BACKGROUND/AIMS: Liver regeneration following chronic injury is associated with inflammation, the proliferation of liver progenitor (oval) cells and fibrosis. Previous studies identified interferon-gamma as a key mediator of oval cell proliferation. Interferon-gamma is known to regulate Th1 cell activities during immune challenge. Therefore, we hypothesised that progenitor cell-mediated regeneration is associated with a Th1 immune response. METHODS: C57Bl/6 (normal Th1 response) and BALB/c mice (deficient in Th1 signalling) were placed on a carcinogenic diet to induce liver injury, progenitor cell proliferation and fibrosis. RESULTS: Serum transaminases and mortality were elevated in BALB/c mice fed the diet. Proliferation of liver progenitor cells was significantly attenuated in BALB/c animals. The pattern of cytokine expression and inflammation differed between strains. Liver fibrosis and hepatic stellate cell activation were significantly inhibited in BALB/c mice compared to C57Bl/6. In addition, interferon-gamma knockout mice also showed reduced fibrosis compared to wild type. These findings are in contrast to published results, in which interferon-gamma is shown to be anti-fibrogenic. CONCLUSIONS: Our data demonstrate that the hepatic progenitor cell response to a CDE diet is inhibited in mice lacking Th1 immune signalling and further show that this inhibition is associated with reduced liver fibrosis.     

The role of hypercoagulability in liver fibrogenesis

The development of hepatic fibrosis on a background of chronic liver injury represents a complex disease trait modulated through the interaction of host genetic factors and environmental influences. Early observations that hepatic inflammation and cirrhosis are associated with the presence of microthrombi within the hepatic vasculature and fibrin/fibrinogen deposition were followed by epidemiological studies showing that carriage of the Factor V Leiden (FvL) mutation, protein C deficiency and increased expression of factor VIII are associated with accelerated progression to cirrhosis in a chronic hepatitis C infection. Additional data suggest that these factors may influence fibrogenesis in many forms of chronic liver disease and extra-hepatic fibrotic processes. Drawing evidence both from liver research and studies of fibrogenesis in other organ systems, two hypotheses may explain how activity of the coagulation cascade influences the rate of hepatic fibrogenesis: tissue ischaemia and parenchymal extinction and direct thrombin mediated stellate cell activation via PAR-1 cleavage. Drawing on preclinical and clinical studies we discuss the evidence for a role for coagulation cascade activity in hepatic fibrogenesis and explore the proposed pathogenic mechanisms that lead to stellate cell activation. The corollary of an association between hypercoagulation and increased fibrosis is that interference with the coagulation cascade may reduce hepatic fibrosis. We conclude this article by examining the implications for future therapeutic intervention.     

Induction of heme oxygenase 1 prevents progression of liver fibrosis in Mdr2 knockout mice

Induction or overexpression of the heme-degrading enzyme, heme oxygenase 1 (HO-1), has been shown to protect mice from liver damage induced by acute inflammation. We have investigated the effects of HO-1 induction in a mouse model of chronic liver inflammation and fibrogenesis with progression to hepatocellular carcinoma (HCC) (Mdr2ko; FVB.129P2-Abcb4(tm1Bor)). HO-1 was induced in vivo by treatment with cobalt protoporphyrin IX, starting at week 5 or 12 of mice lifespan, and continued for 7 weeks. Our results showed that HO-1 induction reduced liver damage and chronic inflammation by regulating immune cell infiltration or proliferation as well as tumor necrosis factor receptor signaling. Fibrosis progression was significantly reduced by HO-1 induction in mice with mild, as well as established, portal and lobular fibrosis. HO-1 induction significantly suppressed hepatic stellate cell activation. During established fibrosis, HO-1 induction was able to revert portal inflammation and fibrosis below levels observed at the start of treatment. Moreover, hepatocellular proliferation and signs of dysplasia were decreased after HO-1 induction. CONCLUSION: Induction of HO-1 interferes with chronic inflammation and fibrogenesis and, in consequence, might delay progression to HCC.     

Chronic ethanol consumption inhibits hepatic natural killer cell activity and accelerates murine cytomegalovirus-induced hepatitis

BACKGROUND: Chronic alcohol drinking accelerates the progression of liver disease in patients with hepatitis viral infection; however, the underlying mechanisms are not fully understood. METHODS: Here, we examined the effects of chronic ethanol feeding on hepatic natural killer (NK) cells and liver injury in 2 murine models of liver injury: injection of synthetic double-stranded RNA polyinosinic-polycytidylic acid (poly I:C), which mimics viral infection, and infection with murine cytomegalovirus (MCMV). Mice were fed the Lieber-DeCarli liquid diet containing 5% (vol/vol) ethanol for 8 weeks, resulting in a significant decrease in the percentage and total number of NK cells in the liver. RESULTS: In control, pair-fed mice, poly I:C injection induced NK cell accumulation in the liver and activated hepatic NK cell cytotoxicity, whereas such induction and activation were diminished in ethanol-fed mice. Treatment with poly I:C also induced expression of NKG2D, granzyme B, perforin, Fas L, TRAIL, and IFN-gamma on liver lymphocytes, which were delayed or reduced in ethanol-treated mice compared with pair-fed mice. In contrast, chronic ethanol feeding did not affect poly I:C-induced mild liver injury. Furthermore, MCMV infection activated hepatic NK cells and induced hepatic inflammation and injury. Chronic ethanol consumption inhibited hepatic NK cell activation during MCMV infection, but enhanced MCMV-induced liver injury, viral titer, and inflammation in the liver. CONCLUSIONS: Taken together, these findings suggest that chronic ethanol consumption decreases hepatic NK activity, thereby accelerating MCMV-induced hepatitis and liver injury.     

Hepatic macrophage migration and differentiation critical for liver fibrosis is mediated by the chemokine receptor C-C motif chemokine receptor 8 in mice

Chemokines critically control the infiltration of immune cells upon liver injury, thereby promoting hepatic inflammation and fibrosis. The chemokine receptor CCR8 can affect trafficking of monocytes/macrophages, monocyte-derived dendritic cells (DCs) and T-helper cell (Th) subsets, but its role in liver diseases is currently unknown. To investigate the functional role of CCR8 in liver diseases, ccr8(-/-) and wild-type (WT) mice were subjected to chronic experimental injury models of carbon tetrachloride (CCl(4) ) administration and surgical bile duct ligation (BDL). CCR8 was strongly up-regulated in the injured liver. Ccr8(-/-) mice displayed attenuated liver damage (e.g., ALT, histology, and TUNEL) compared to WT mice and were also protected from liver fibrosis in two independent injury models. Flow cytometry revealed reduced infiltrates of liver macrophages, neutrophils and natural killer cells, whereas hepatic CD4(+) T cells increased. The main CCR8-expressing cells in the liver were hepatic macrophages, and CCR8 was functionally necessary for CCL1-directed migration of inflammatory but not for nonclassical monocytes into the liver. Moreover, the phenotype of liver macrophages from injured ccr8(-/-) animals was altered with increased expression of DC markers and enhanced expression of T-cell-attracting chemokine macrophage inflammatory protein 1-alpha (MIP-1α/CCL3). Correspondingly, hepatic CD4(+) T cells showed increased Th1 polarization and reduced Th2 cells in CCR8-deficient animals. Liver fibrosis progression, but also subsequent T-cell alterations, could be restored by adoptively transferring CCR8-expressing monocytes/macrophages into ccr8(-/-) mice during experimental injury. CONCLUSIONS: CCR8 critically mediates hepatic macrophage recruitment upon injury, which subsequently shapes the inflammatory response in the injured liver, affecting macrophage/DC and Th differentiation. CCR8 deficiency protects the liver against injury, ameliorating initial inflammatory responses and hepatic fibrogenesis. Inhibition of CCR8 or its ligand, CCL1, might represent a successful therapeutic target to limit liver inflammation and fibrosis progression.     

Role of iron load on fibrogenesis in chronic hepatitis C

BACKGROUND/AIMS: In chronic viral hepatitis, an enhanced iron load is related to lower response to interferon. Furthermore, iron, through the production of oxygen radicals, may stimulate hepatocyte necrosis and the activation of cells responsible for synthesis and deposition of extracellular matrix. We investigated the relationship between iron load, evaluated by serum assays, and liver fibrogenesis in chronic active viral hepatitis. METHODOLOGY: Serum iron, ferritin, transferrin saturation and serum markers of hepatic fibrogenesis (Laminin and the amino-terminal peptide of procollagen III-NPIIIP-) were assayed in 102 patients (47 females, 55 males, mean age 42.48 years) affected by chronic hepatitis C virus and in 81 healthy controls (47 males, 34 females). In hepatitis C virus patients (studied before alpha-interferon treatment) a semiquantitative score for portal inflammation, necrosis and fibrosis was applied to liver biopsy. RESULTS: Serum indices of iron load were higher in hepatitis C virus patients than in controls, and were higher in cirrhotic than in chronic hepatitis cases. Ferritin and serum iron were positively correlated with NPIIIP and laminin; moreover cases with ferritin levels over the normal limit for sex and age had higher levels of NPIIIP and laminin than cases with normal or poor iron status. CONCLUSIONS: Our data suggest that even a mild increase of iron load stimulates hepatic fibrogenesis, probably adding oxygen free radical injury to the damage of viral infection.     

PNPLA3 I148M polymorphism and progressive liver disease

The 148 Isoleucine to Methionine protein variant(I148M)of patatin-like phospholipase domain-containing 3(PNPLA3),a protein is expressed in the liver and is involved in lipid metabolism,has recently been identified as a major determinant of liver fat content.Several studies confirmed that the I148M variant predisposes towards the full spectrum of liver damage associated with fatty liver:from simple steatosis to steatohepatitis and progressive fibrosis.Furthermore,the I148M variant represents a major determinant of progression of alcohol related steatohepatitis to cirrhosis,and to influence fibrogenesis and related clinical outcomes in chronic hepatitis C virus hepatitis,and possibly chronic hepatitis B virus hepatitis,hereditary hemochromatosis and primary sclerosing cholangitis.All in all,studies suggest that the I148M polymorphism may represent a general modifier of fibrogenesis in liver diseases.Remarkably,the effect of the I148M variant on fibrosis was independent of that on hepatic steatosis and inflammation,suggesting that it may affect both the quantity and quality of hepatic lipids and the biology of non-parenchymal liver cells besides hepatocytes,directly promoting fibrogenesis.Therefore,PNPLA3 is a key player in liver disease progression.Assessment of the I148M polymorphism will possibly inform clinical practice in the future,whereas the determination of the effect of the 148M variant will reveal mechanisms involved in hepatic fibrogenesis.     

Hepatic alpha-smooth muscle actin expression in hepatitis C patients before and after interferon therapy

BACKGROUND/AIMS: The mechanism of hepatic fibrogenesis with chronic viral hepatitis is not well understood. Persistent activation of hepatic stellate cells is felt to play a role in the development of fibrogenesis and progression to cirrhosis. METHODOLOGY: We determined the expression of hepatic alpha-smooth muscle actin, a marker of hepatic stellate cell activation, in 29 patients with chronic hepatitis C and varying degrees of liver injury and fibrosis. In addition to a baseline evaluation, we assessed the effect of interferon therapy on alpha-smooth muscle actin expression in 11 patients, including 6 with a sustained response to therapy. Specimens were evaluated by light microscopy for grade of inflammation and stage of fibrosis. Expression of alpha-smooth muscle actin was assessed semiquantitatively by immunohistochemical staining. RESULTS: At baseline, all patients had alpha-smooth muscle actin expressed within the liver without an obvious correlation with the severity of liver injury. However, among sustained responders, a reduction in hepatic necroinflammatory activity was associated with a trend towards a decrease in alpha-smooth muscle actin expression. This however did not reach statistical significance. CONCLUSIONS: Hepatic alpha-smooth muscle actin expression, as a marker of hepatic stellate cell activation appears reversible and tends to correlate with necroinflammatory activity.     

Hepatoprotective role of ganoderma lucidum polysaccharide against BCG—induced immune liver injury in mice

AIM：To examine the effect of ganoderma lucidum polysaccharide(GLP)on the immune liver injury induced by BCG infection,and investigate the relationship between degrees of hepatic damage and NO production in mice.METHODS:Immune hepatic injury was markedly induced by BCG-pretreatment(125mg·kg^-1,2-week,iv)or by BCG-pretreatment plus lipopolysaccharide(LPS,125μg·kg^-1,12-hour,iv)in mice in vivo.Hepatocellular damage induced by BCG-pretreated plus inflammatory cytokines mixture(CM).which was includid TNF-α,IL-1β,IFN-γand LPSin culture medium in vitro.Administration of GLP was performed by oral or incubating with culture medium at immune stimuli simultaneity.Liver damage was determined by activity of alaine aminotransferase(ALT)in serum and in hepatocytes cultured supernatant,by liver weight changes and histopathlogical examination.NO production in the cultured supernatant was determined by the Griess reaction.Moreover,inducible nitric oxide synthase(iNOS)protein expression was also examinated by immunohistochemical method.RESULTS:Immune hepatic injury was markedly induced by BCG or BCGplus inflammatory cytokines in BALB/c mice in vivoand in vito.Under BCG-stimulated condition,augment of the liver weight and increase of the serum/supernatant ALTlevel were observed,as well as granuloma forming and inflammatory cells soakage were observed by microscopic analysis within liver tissues.Moreover.NO production was also increased by BCGor/and CM stimuli in the culture supernatant ,and a lot of iNOS positive staining was observed in BCG-prestimulated hepatic sections.Applicatin of GLP significantly mitigated hepatic tunefaction,decreased ALT enzyme release and NO production in serum/supernatant,improved the pathological changes of chronic and acute inflammation induced by BCG-stimuli in mice.Moreover.the immunohistochemical result showed that GLP inhibited iNOS protein expression in BCG-immune hepatic damage model.CONCLUSION:The present study indicates that NO participates in immune liver injury in duced by Mycobacterium bovisBCG infection.The mechanisms of protective roles by GLPfor BCG-induced immune liver injury may be due to influence NO production in mice.     

The role of leptin in progression of non-alcoholic fatty liver disease.

Since non-alchoholic steatohepatitis (NASH) is often accompanied with metabolic syndrome comprising obesity, type-2 diabetes and hypertension, it is hypothesized that adipocytokines, insulin resistance and autonomic nervous system play crucial roles in disease progression of NASH. On the other hand, hepatic stellate cells (HSCs) have been shown to produce leptin when they get activated during hepatic fibrogenesis. Therefore, we investigated the role of leptin in fibrogenesis in the liver. Xenobiotics-induced liver fibrosis was extremely diminished in ob/ob mice and Zucker (fa/fa) rats, an inborn leptin- and leptin receptor (Ob-R)-deficient animal, respectively. Further, leptin increased transforming growth factor (TGF)-beta mRNA in isolated sinusoidal endothelial cells and Kupffer cells, suggesting that leptin promotes hepatic fibrogenesis through up-regulation of TGF-beta in the liver. Moreover, leptin augmented PDGF-dependent proliferation of HSCs by enhancing downstream intracellular signaling pathways via mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K)/Akt. Taken together, it is postulated that leptin acts as a profibrogenic cytokine in sinusoidal microenvironment. These findings indicate that leptin is one of the key regulators for inflammation and progression of fibrosis in various chronic liver diseases including NASH.     

Role of the endocannabinoid system in alcoholic liver disease

Alcohol abuse is a major cause of liver fibrosis and cirrhosis in developed countries. Alcoholic liver disease (ALD) is distinctively characterized by a pronounced inflammatory response due to elevated gut-derived endotoxin plasma levels, an augmented generation of oxidative stress with pericentral hepatic hypoxia and the formation of noxious ethanol metabolites (e.g. acetaldehyde or lipid oxidation products). These factors, based on a complex network of cytokine actions, together result in increased hepatocellular damage and activation of hepatic stellate cells, the key cell type of liver fibrogenesis. Recent studies suggest that the endocannabinoid system is a signaling system that also plays an important role in the pathogenesis of ALD. A study comparing chronic alcohol administration in cannabinoid receptor (CB) 1 or CB2 knockout versus wild-type mice revealed that CB1 signaling aggravated hepatic steatosis and fibrogenesis whereas CB2 protected the liver from ALD. These data suggested a protective role of CB2 (in contrast to CB1) in ALD. Similar results were found in global or hepatocyte-specific CB1 knockout mice that were resistant to ethanol-induced steatosis. Moreover, ethanol feeding upregulated the endocannabinoid 2-arachidonoyl glycerol and its biosynthetic enzyme diacylglycerol lipase-β selectively in hepatic stellate cells and subsequently increased expression of CB1 receptors in hepatocytes of wild-type mice leading to CB1-dependent hepatic steatosis by activation of lipogenic pathways. This ethanol-induced upregulation of CB1 receptors was partly dependent on the ethanol metabolite acetaldehyde. Thus, the hepatic endocannabinoid system offers emerging options for therapeutic exploitation not only for liver disease in general, but also for ALD.     

炎症小体与慢性肝脏疾病

多种慢性肝脏疾病都与组织的无菌性炎症有关。核苷酸结合寡聚化结构域样受体家族形成的多蛋白复合物——炎症小体,作为炎症反应的核心,能被多种外源或内源性刺激激活,引起下游炎症因子分泌,诱发炎症反应,其过度激活会造成组织损伤。现已证实炎症小体在酒精性和非酒精性脂肪性肝病、肝脏缺血再灌注损伤及药物性肝损伤等疾病中起关键作用,是肝脏发生纤维化和癌变的决定因素之一。本文就炎症小体的结构、活化信号及激活通路、调节机制及其与慢性肝脏疾病关系的研究进展作一综述,以期为慢性肝脏疾病的治疗提供新的方向和靶点。     

High,but not low,dietary retinoids aggravate manifestation of rat liver fibrosis

BACKGROUND: Although there is strong implication that retinoids regulate Ito cell proliferation and collagen synthesis, results from in vivo studies on the relationship between vitamin A and liver fibrosis are conflicting. The present study focuses on the role of vitamin A in carbon tetrachloride (CCl4)-induced fibrosis by chronic feeding of rats with either a vitamin A-supplemented or -depleted diet. METHODS AND RESULTS: In animals with high dietary hepatic retinoid levels, liver fibrosis was more pronounced and was associated with an increased CCl4-toxicity resulting in high mortality (73%). Enhanced liver fibrosis was confirmed by in vivo fluorescence microscopic determination of both collagen deposits (7.4 +/- 1.1 vs 3.9 +/- 0.3% in high vitamin A diet-fed and standard diet-fed fibrotic animals, respectively; P < 0.05) and rarefication of sinusoids (1.5 +/- 0.2 vs 2.4 +/- 0.2 sinusoids/200 microm in high vitamin A diet-fed and standard diet-fed fibrotic animals, respectively; P < 0.05). It was further associated with decreased bile flow and increased parenchymal cell damage. CCl4 reduced hepatic retinoid levels in high vitamin A diet-fed animals, but restored hepatic retinoid levels in animals fed with a vitamin A-deficient diet, implying major interference of vitamin A metabolism with hepatotoxic agents such as CCl4. Low vitamin A feeding did not modulate liver fibrogenesis and caused no mortality. CONCLUSIONS: These results show that the vitamin A status of the liver plays an important role in liver fibrogenesis. While dietary vitamin A shortage does not promote liver fibrogenesis, high levels of vitamin A have the potential to increase systemic and hepatic toxicity of CCl4. Thus, the narrow therapeutic window for nutritional vitamin A substitution must take into account that liver fibrotic patients may display enhanced susceptibility to the adverse effects of vitamin A.     

Hepatic stellate cell activation and liver fibrosis are associated with necroinflammatory injury and Th1-like response in chronic hepatitis C.

BACKGROUND/AIMS: The involvement of a direct viral cytopathic effect or an immune-mediated mechanism in the progression of hepatic damage in chronic hepatitis C is controversial. The type of immune response is itself a matter of controversy, and histological data are lacking. The aim of this study was to identify the factors associated with the progression of liver injury in 30 HCV/RNA-positive untreated patients with chronic hepatitis. METHODS: Necroinflammatory and architectural damage were evaluated using Ishak's score. Activated hepatic stellate cells (HSC) were visualized by immunohistochemistry for alpha-smooth muscle actin (alphaSMA) and quantitated by morphometry. Plasma HCV/RNA was evaluated using a competitive RT-PCR method. To study the type of immune response involved in the progression of liver injury, interferon gamma (IFNgamma)-positive cells (as expression of a Th1-like response) were evaluated by immunohistochemistry and quantitated by morphometry. RESULTS: HSC were mostly detected close to areas of lobular necroinflammation or lining fibrotic septa. The alphaSMA- and Sirius Red-positive parenchyma correlated significantly with necroinflammatory and architectural scores. IFNgamma-positive cells were detected in periportal areas associated with the inflammatory infiltrates and significantly correlated with architectural damage. No relationship was found between the histological features of liver injury and viral load. CONCLUSIONS: HSC activation and progression of liver injury are unrelated to viral load but associated with a Th1-like response, a plausible target for the treatment of chronic hepatitis C.     

Protective effects of trichostatin A on liver injury in septic mice

Aim:  Acetylation is emerging as a crucial post-translational modification in controlling the expression of eukaryotic genes. Histone deacetylase (HDAC) inhibitors, developed as antitumor reagents, have recently exhibited novel anti-inflammatory properties. In the present study, the influence of HDAC inhibitor on hepatic injury during sepsis was investigated.
Methods:  Trichostatin A (TSA), a potent HDAC-specific inhibitor, was administrated to mice with cecal ligation and puncture (CLP)-induced sepsis. The degree of hepatic injury and inflammation was assessed subsequently.
Results:  The results indicated that TSA effectively protected liver from CLP-induced injury as evidenced by decreased serum aminotransferases (alanine and aspartate) levels, reduced malondialdehyde (MDA) content in liver homogenates and improved histological damage. The dampened liver injury was accompanied by lower myeloperoxidase (MPO) activity and suppressed expression of intercellular adhesion molecule-1 (ICAM-1) in liver tissue. In addition, the concentrations of both interleukin (IL)-6 and IL-10 in serum or hepatic homogenates were also decreased in TSA-treated septic mice.
Conclusion:  These data indicate that HDAC inhibitor TSA effectively attenuates liver injury during sepsis and these effects seem to rely on reduced inflammatory mediator production. These findings suggest that novel anti-inflammatory drugs targeting HDAC might offer promising therapeutic intervention for controlling the dysregulated inflammation.     

The epidermal growth factor receptor ligand amphiregulin participates in the development of mouse liver fibrosis

The hepatic wound-healing response to chronic noxious stimuli may lead to liver fibrosis, a condition characterized by excessive deposition of extracellular matrix. Fibrogenic cells, including hepatic stellate cells and myofibroblasts, are activated in response to a variety of cytokines, growth factors, and inflammatory mediators. The involvement of members of the epidermal growth factor family in this process has been suggested. Amphiregulin (AR) is an epidermal growth factor receptor (EGFR) ligand specifically induced upon liver injury. Here, we have addressed the in vivo role of AR in experimental liver fibrosis. To this end, liver fibrosis was induced in AR+/+ and AR-/- mice by chronic CCl(4) administration. Histological and molecular markers of hepatic fibrogenesis were measured. Additionally, the response of cultured human and mouse liver fibrogenic cells to AR was evaluated. We observed that AR was expressed in isolated Kupffer cells and liver fibrogenic cells in response to inflamatory stimuli and platelet-derived growth factor, respectively. We demonstrate that the expression of alpha-smooth muscle actin and collagen deposition were markedly reduced in AR-/- mice compared to AR+/+ animals. AR-/- mice also showed reduced expression of tissue inhibitor of metalloproteinases-1 and connective tissue growth factor, two genes that responded to AR treatment in cultured fibrogenic cells. AR also stimulated cell proliferation and exerted a potent antiapoptotic effect on isolated fibrogenic cells. CONCLUSION: These results indicate that among the different EGFR ligands, AR plays a specific role in liver fibrosis. AR may contribute to the expression of fibrogenic mediators, as well as to the growth and survival of fibrogenic cells. Additionally, our data lend further support to the role of the EGFR system in hepatic fibrogenesis.     

IL-18 and IL-12 induce intestinal inflammation and fatty liver in mice in an IFN-gamma dependent manner

BACKGROUND: In murine models of inflammatory bowel disease, colonic inflammation is considered to be caused by an aberrant Th1-type immune response. AIM: To investigate if systemic administration of interleukin (IL)-12 and IL-18 to wild-type BALB/c mice induces liver injury and intestinal inflammation, and if pathological changes are observed, what cytokines are involved. METHODS: Mice (BALB/c-wild-type (wt), MRL-lpr/lpr, BALB/c-interferon gamma knock out (IFN-gamma KO), C57BL/6-inducible nitric oxide synthase (iNOS) KO, and BALB/c tumour necrosis factor alpha (TNF-alpha) KO) were injected intraperitoneally each day with IL-12 (20 ng/g/mouse) and/or IL-18 (200 ng/g/mouse). RESULTS: Administration of IL-12 and IL-18 to BALB/c-wt mice induced prominent intestinal mucosal inflammation and fatty liver, leading to piloerection, bloody diarrhoea, and weight loss. IL-12 and IL-18 induced striking elevations in serum levels of IFN-gamma that caused NO production, although increased NO had no exacerbating effect on mice. Moreover, iNOS KO mice, or MRL lpr/lpr mice lacking functional Fas were equally susceptible to IL-12 and IL-18. Administration of IL-12 and IL-18 did not induce TNF-alpha production in wild-type mice, and the same treatment to TNF-alpha KO mice induced intestinal mucosal inflammation. Furthermore, they had diffuse and dense infiltration of small fat droplets in their hepatocytes associated with an increase in serum levels of liver enzymes. In contrast, the same treatment in IFN-gamma KO BALB/c mice and iNOS KO mice did not induce these changes. CONCLUSIONS: Our study strongly indicates that IL-18 together with IL-12 induces intestinal mucosal inflammation in an IFN-gamma dependent but TNF-alpha, NO, and Fas ligand independent manner, and fatty liver is dependent on IFN-gamma and NO.