Monika Ledermann

Pharmacological Inhibition of Integrin αvβ3 Aggravates Experimental Liver Fibrosis and Suppresses Hepatic Angiogenesis

The vitronectin receptor integrin αvβ3 promotes angiogenesis by mediating migration and proliferation of endothelial cells, but also drives fibrogenic activation of hepatic stellate cells (HSCs) in vitro. Expecting antifibrotic synergism, we studied the effect of αvβ3 inhibition in two in vivo models of liver fibrogenesis. Liver fibrosis was induced in rats by way of bile duct ligation (BDL) for 6 weeks or thioacetamide (TAA) injections for 12 weeks. A specific αvβ3 (αvβ5) inhibitor (Cilengitide) was given intraperitoneally twice daily at 15 mg/kg during BDL or after TAA administration. Liver collagen was determined as hydroxyproline, and gene expression was quantified by way of quantitative polymerase chain reaction. Liver angiogenesis, macrophage infiltration, and hypoxia were assessed by way of CD31, CD68 and hypoxia‐inducible factor‐1α immunostaining. Cilengitide decreased overall vessel formation. This was significant in portal areas of BDL and septal areas of TAA fibrotic rats and was associated with a significant increase of liver collagen by 31% (BDL) and 27% (TAA), and up‐regulation of profibrogenic genes and matrix metalloproteinase‐13. Treatment increased gamma glutamyl transpeptidase in both models, while other serum markers remained unchanged. αvβ3 inhibition resulted in mild liver hypoxia, as evidenced by up‐regulation of hypoxia‐inducible genes. Liver infiltration by macrophages/Kupffer cells was not affected, although increases in tumor necrosis factor α, interleukin‐18, and cyclooxygenase‐2 messenger RNA indicated modest macrophage activation. Conclusion: Specific inhibition of integrin αvβ3 (αvβ5) in vivo decreased angiogenesis but worsened biliary (BDL) and septal (TAA) fibrosis, despite its antifibrogenic effect on HSCs in vitro. Angiogenesis inhibitors should be used with caution in patients with hepatic fibrosis. (HEPATOLOGY 2009.)

Potent antifibrotic activity of mTOR inhibitors sirolimus and everolimus but not of cyclosporine A and tacrolimus in experimental liver fibrosis

BACKGROUND & AIMS Recurrence of chronic hepatitis C and progressive fibrosis in liver transplants is frequent and impairs both graft and patient survival. Whether or not the choice of immunosuppression affects progression of fibrosis remains unclear. The aim of the present study was to compare the potential of the commonly used immunosuppressants to halt experimental liver fibrosis progression. METHODS To induce liver fibrosis, rats underwent bile duct ligation and treatment with sirolimus (2mg/kg), everolimus (3mg/kg), tacrolimus (1mg/kg), and cyclosporin A (10mg/kg) daily for 5 weeks. Fibrosis, inflammation, and portal pressure were evaluated by histology, hydroxyproline levels, morphometry, hemodynamics, and hepatic gene expression. RESULTS Sirolimus and everolimus decreased fibrosis up to 70%, improved portal pressure, reduced ascites, and showed potent down-regulation of pro-fibrogenic genes, paralleled by a strong increase in matrix degradation (collagenase) activity; in contrast, tacrolimus and cyclosporine A had no or even aggravating effects on liver fibrosis in rats. CONCLUSIONS mTOR inhibition by sirolimus and everolimus in experimental liver fibrosis associates with significantly less fibrosis progression and portal hypertension than treatment with calcineurin inhibitors tacrolimus and cyclosporine A. These data suggest that the selection of the immunosuppressant could impact the recurrence of fibrosis in liver allografts.

Expression and activity of the cytochrome P450 2E1 in patients with nonalcoholic steatosis and steatohepatitis

Background/Aims: Nonalcoholic steatohepatitis (NASH) and nonalcoholic fatty liver (NAFL) have a different prognosis and should be dealt with differently. The pathogenesis of NASH implicates the overexpression of cytochrome P450 2E1 (CYP2E1). We investigated whether the noninvasive determination of CYP2E1 activity could replace a liver biopsy in order to differentiate NASH from NAFL.

Effects on hepatocellular carcinoma of doxorubicin-loaded immunoliposomes designed to target the VEGFR-2

To maintain a tumour vasculature in proportion of the tumour growth, the endothelial cells proliferate and up-regulate the expression of the VEGF receptor 2 (VEGFR-2), whose expression is restricted to this cell type. This specificity implies that one therapeutically target the tumour endothelium. We investigated the use of immunoliposomes (IL), containing conjugated Fab′ fragments of the monoclonal rat anti-VEGFR-2 antibody DC101 (DC101-IL) to cargo doxorubicin to the tumour endothelium. In vitro, fluorescein-labelled IL displayed a 7 fold better binding to VEGFR-2-positive 293T cells in comparison to unspecific liposomes. Balb/C mice were injected subcutaneously with syngeneic hepatocellular carcinoma cells. One set of animals was treated with DC101-IL filled with doxorubicin when the tumours were bigger than 400 mm3. A specific delivery of doxorubicin to endothelial cells of the tumour vessels could be demonstrated by the red fluorescence of doxorubicin with laser scanning microscopy, but neither a delay of tumour growth nor a shrinking of the tumour mass was observed. Yet necrosis in the tumours treated with doxorubicin containing vehicles was larger than in the tumours of the control groups. A second set of animals was treated with DC101-IL filled with doxorubicin when the tumours were smaller than 1 mm3. DC101-IL filled with doxorubicin led to a significant delay in tumour growth up to 7 weeks compared to empty DC101-IL, free doxorubicin, and HEPES/Glucose (HEPES/Glucose vs. DOX-DC101-IL, p = 0.001; unpaired, two-tailed Students t-test) and to a higher amount of necrotic areas in the tumours (p = 0.053; 1 way ANOVA with 4 groups). These findings suggest that IL designed to bind specifically to VEGFR-2 can be used to deliver doxorubicin to the tumour endothelium and may impair the “angiogenic switch” of the tumours.

Relationship between hepatic mitochondrial functions in vivo and in vitro in rats with carbon tetrachloride-induced liver cirrhosis.

BACKGROUND/AIMS The metabolic capacity of liver mitochondria is impaired in rats with carbon tetrachloride (CCl4)-induced cirrhosis. These studies were performed to find out whether benzoate and/or palmitate are suitable substrates for assessing hepatic mitochondrial function in vivo. METHODS In vivo metabolism of benzoate and 1-14C-palmitate was assessed by monitoring urinary excretion of hippurate and exhalation of 14CO2, respectively, in cirrhotic and control rats (n=8 for each group). Isolation of liver mitochondria, and in vitro benzoate and palmitate metabolism were performed by methods published previously. The hepatic content of mitochondria was assessed by stereological analysis of the volume of hepatocytes and by biochemical determination, using the activity of citrate synthase. RESULTS Renal excretion of hippurate following i.p. administration of benzoate was reduced in cirrhotic rats (64+/-15 vs. 85+/-14% of administered dose over 24 h), and showed a linear correlation with hippurate formation by isolated mitochondria. The activities of benzoyl-CoA synthase and benzoyl-CoA:glycine N-acyltransferase were reduced by approximately 60%, and the coenzyme A content by 50% in hepatic mitochondria from cirrhotic rats, explaining impaired hippurate formation. Peak exhalation of 14CO2 after i.p. administration of 1-14C-palmitate was reduced by 44% and the area under the 14CO2 exhalation-time curve by 34% in cirrhotic rats. Peak 14CO2 exhalation revealed a linear correlation with oxidative metabolism of palmitoylcarnitine in isolated mitochondria. Both in vivo benzoate and palmitate metabolism showed a linear correlation with the volume fraction of hepatocytes. The mitochondrial protein content was reduced in cirrhotic rats per g liver and per liver but equal to control rats per volume of hepatocytes. CONCLUSIONS In vivo metabolism of both palmitate and benzoate reflects hepatic mitochondrial function in rats with CCl4-induced cirrhosis. Hepatic mitochondrial function is impaired in rats with CCl4-induced cirrhosis due to both reduced mitochondrial volume per liver and impaired metabolism of the remaining mitochondria. In contrast to rats with secondary biliary cirrhosis, rats with CCl4-induced cirrhosis showed no hepatic mitochondrial proliferation to counteract reduced mitochondrial function.

Endothelial nitric oxide synthase is not essential for the development of fibrosis and portal hypertension in bile duct ligated mice

Abstract: Background/Aims: It is postulated that nitric oxide (NO) is responsible for the hyperdynamic circulation of portal hypertension. Therefore, we investigated induction of fibrosis and hyperdynamic circulation in endothelial NO synthase knock‐out (KO) mice.

82 ABLATION OF HISTIDINE TRIAD NUCLEOTIDE-BINDING PROTEIN-1 (HINT1) INCREASES SENSITIVITY TO HEPATOCELLULAR CARCINOMA

2239 Background and aim: HINT1 is a nucleotide binding protein with adenosine-5’ phosphoraminidate hydrolase activity. In vitro studies revealed that Hint1 1) up-regulates p53 and the pro-apoptotic factor Bax and 2) inhibits T-cell factor/beta-catenin-mediated transcription of Wnt target genes. In vivo, mice with an homozygous-deletion of Hint1 spontaneously develop more tumors than control mice after 2 years. The aim of this study was to investigate the susceptibility of Hint1-/- mice to hepatocarcinogenesis.
 Methods: Hint1-/- and C57BL6 mice (2 weeks old) were subjected to a diethylnitrosamine/phenobarbital tumour-induction protocol: 1 intraperitoneal injection of diethylnitrosamine; 2 weeks later, drinking water supplemented with 0.05% phenobarbital. Animals were harvested 10, 20 and 30 weeks after injection (10/group). The number and volume of tumors were determined in vivo by MR imaging using Primovist® contrast then livers were dissected. The histology was analyzed by H&E staining. The expression of glutamine synthase, a marker for activation of the Wnt pathway was analysed by immunohistochemistry.
 Results: After 20 weeks, MR imaging and liver dissection confirmed hepatic tumors in 30% of control and 70% of Hint1-/- mice but no tumors after 10 weeks in either group. The tumors were more numerous in the Hint1-/- group (1.6/mouse) than in controls (0.6/mouse). After 30 weeks, all animals developed tumors, which were more numerous in the Hint1-/- group (11.25 nodules/ mouse) than in controls (8.25 nodules/mouse) and larger in Hint1-/- mice (89.14 mm3 at 20 weeks and 178 mm3 at 30 weeks) than in controls (