Development of a large animal model of cirrhosis and portal hypertension using hepatic transarterial embolization: a study in swine

PURPOSE

To develop a clinically relevant porcine model of liver cirrhosis with portal hypertension by means of hepatic transarterial embolization.

MATERIALS AND METHODS

Institutional animal care and use committee approval was obtained for all experiments. Pigs received transcatheter arterial infusion of a 3:1 mixture of iodized oil and ethanol into the hepatic artery in volumes of 16 mL in group 1 (n = 4), 28 mL in group 2 (n = 4), and 40 mL in group 3 (n = 4) with intent of bilobar distribution. Hepatic venous pressure gradient (HVPG) measurement, liver function tests, and volumetry were performed at baseline, at 2 weeks, and before necropsy.

RESULTS

Cirrhosis was successfully induced in three animals that received 16 mL of the embolic mixture and in all four animals that received 28 mL. The animals in the 40-mL group did not recover from the procedure and were euthanized within 48 h. Increases in HVPG after 6-8 weeks versus baseline reached statistical significance (P < .05). Correlation between degree of fibrosis and volume of embolic agent did not reach statistical significance, but there was a trend toward increased fibrosis in the 28-mL group compared with the 16-mL group.

CONCLUSIONS

Transcatheter hepatic arterial embolization can be used to create a reliable and reproducible porcine model of liver cirrhosis and portal hypertension.

The role of lipophilic bile acids in the development of cirrhotic cardiomyopathy

Marked hemodynamic changes occur in humans and experimental animals with cirrhotic liver disease. In the heart, basal contractility, responsiveness to beta-adrenoceptor activation, and excitation-contraction coupling (ECC) are negatively affected in models of cirrhosis and portal hypertension with portosystemic shunting (PVS), and comprise what has been called cirrhotic cardiomyopathy. These effects are accompanied by elevated circulating levels of bile acids. We investigated whether elevated bile acids act as a myocardial toxicant by exposing cardiac muscle in vitro to bile acids and compared these results with two models of cirrhotic cardiomyopathy with elevated bile acids: CCl4-induced cirrhosis and PVS. Cholic acid, a lipophilic bile acid, produced a decrease in basal cardiac contractility and responsiveness to beta-adrenoceptor activation, both of which appeared to result from altered ECC. beta-Adrenoceptor density and signaling were unaffected. Acutely, ursodeoxycholic acid, a more hydrophilic bile acid, had no effect. Cirrhosis produced a decrease in basal force, depressed beta-adrenoceptor responsiveness, and altered ECC similar to cholic acid. However, cirrhosis also altered beta-adrenoceptor signaling including decreases in cyclic AMP formation, expression of the stimulatory G protein, GS, and beta-adrenoceptor density. Displacement of lipophilic bile acids by chronic administration of ursodeoxycholic acid to rats during the development of cirrhotic cardiomyopathy produced by PVS produced attenuation of the effect on ECC. These results suggest a possible role for lipophilic bile acids in some, but not all of the myocardial consequences of chronic portal vein stenosis and CCl4-induced cirrhosis.

Disruption of the growth hormone--signal transducer and activator of transcription 5--insulinlike growth factor 1 axis severely aggravates liver fibrosis in a mouse model of cholestasis

Growth hormone (GH) resistance and low serum levels of insulinlike growth factor 1 (IGF-1) are common features in human liver fibrosis and cirrhosis. Signal transducer and activator of transcription 5 (STAT5) controls several vital functions in the liver, including GH-mediated transcription of IGF-1. To investigate the role of STAT5 in liver fibrogenesis, we specifically deleted the Stat5a/b locus both in hepatocytes and cholangiocytes in the multidrug resistance gene 2 knockout (Mdr2(-/-)) mouse model of cholestasis. Double knockout mice develop an early and severe liver fibrosis phenotype, accompanied by perturbed expression of key regulators of bile acid homeostasis. Deletion of Stat5 resulted in GH resistance, and IGF-1 levels in serum were undetectable. We could observe reduced expression of important hepatoprotective genes, such as epidermal growth factor receptor (Egfr), hepatocyte nuclear factor 6 (Hnf6), prolactin receptor (Prlr), and leukemia inhibitory factor receptor (Lifr) as well as increased numbers of apoptotic hepatocytes.

CONCLUSION

Our data suggest that loss of STAT5 sensitizes hepatocytes to bile acid-induced damage and apoptosis caused by disruption of GH-induced transcription of Igf-1 and down-regulation of hepatoprotective genes. These findings could contribute to the understanding of liver fibrosis and future treatment strategies for liver fibrosis.

[Comparison of the pathogenesis of liver fibrosis induced by pig serum exposure and bile duct ligation in rats]

OBJECTIVE

To observe the occurrence and progression of liver fibrosis induced by pig serum exposure and bile duct ligation, and analyze the relationship between hepatic inflammation and liver fibrosis.

METHODS

Chronically immune-mediated liver fibrosis was induced in rats by weekly injection of pig serum (IPS) into the peritoneal cavity at 3 ml/kg for 12 weeks. Cholestatic fibrosis was induced by common bile duct ligation (BDL). The Knodell score was used to evaluate the histological changes in the liver, and immunohistochemistry was performed using anti-SMA, anti-ED1, anti-CK7, and anti-CD45 antibodies. Quantitative real time PCR (qPCR) analysis was employed to quantify the mRNA expression of the genes related to inflammation, including interleukin-1beta (IL-1beta), IL-6, monocyte chemotactic protein-1, tumor necrosis factor-alpha, regulated upon activation normal T cell expressed and secreted (RANTES), transforming growth factor-beta, platelet-derived growth factor A, as well as the genes associated with fibrogenesis, namely collagen 1, alphaSMA, MMP-9 and TIMP-1.

RESULTS

Knodell scores for periportal necrosis, intralobular degeneration and focal necrosis, and portal inflammation were all significantly higher in the BDL group than in the IPS group (P<0.01), whereas the scores for fibrosis was higher in the IPS group (P<0.05). Immunohistochemistry showed obvious inflammation with numerous alphaSMA-positive cells in the liver of the rats in BDL group; the liver of the rats in IPS group showed numerous alphaSMA-positive myofibroblasts with limited inflammatory cell infiltration. qPCR demonstrated a significant up-regulation of the genes related to extracellular matrix remodeling such as collagen 1 (P<0.01), alphaSMA (P<0.01), MMP-9 (P<0.01) and TIMP-1 (P<0.01) in the rat liver in IPS group compared with those in the normal control group, and the mRNA expressions of the inflammation-related cytokines, except for RANTES, were comparable with those in the control. In contrast, the BDL group showed a significant up-regulation of all the pro-inflammatory genes examined with also increased expression of the fibrogenesis-related genes (P<0.05).

CONCLUSION

Liver fibrosis induced by IPS is characterized by active ECM remodeling in the absence of obvious inflammation, indicating that chronic development of liver fibrosis can be independent of active hepatic inflammation. BDL-induced liver fibrosis highlights obvious inflammation and fibrous proliferation in the liver.

[Effect of beta-catenin on the activation of hepatic stellate cells induced by transforming growth factor-beta1]

OBJECTIVE

To investigate the effect of beta-catenin on the activation of hepatic fibrosis by transforming growth factor-beta 1 (TGFbeta1).

METHODS

The recombinant expression plasmids pcDNA3.1(+)-beta-catenin and pEGFP-N1 were cotransfected into cultured HSC-T6 cells. The expression of smad3, beta-catenin and alpha-SMA, beta-catenin protein in TGFbeta1 treated HSC-T6 cells were detected by RT-PCR and Western-blot.

RESULTS

The expression of smad3 and beta-catenin in the co-transfected cells was higher than that in the untransfected cells (smad3 mRNA were 0.642 +/- 0.011, 0.501 +/- 0.021, 0.511 +/- 0.019, 0.356 +/- 0.017, respectively, F = 135.304, P < than 0.05. beta-catenin mRNA were 0.783 +/- 0.021, 0.543 +/- 0.033, 0.538 +/- 0.024, 0.212 +/- 0.019, respectively, F = 267.340, P < than 0.05. smad3 protein were 0.892 +/- 0.012, 0.124 +/- 0.011, 0.130 +/- 0.021, 0.003 +/- 0.001, F = 2823.813, P < l than 0.05. beta-catenin protein were 0.921 +/- 0.020, 0.210 +/- 0.010, 0.208 +/- 0.008, 0.002 +/- 0.001, respectively, F = 3440.982, P < than 0.05). The expression of beta-catenin and smad3 protein had a positive correlation with the level of alpha-SMA protein in cells (r = 0.901, P < than 0.01; r = 0.939, P < than 0.01).

CONCLUSIONS

Expression of smad3/alpha-SMA/beta-catenin is increased in the cultured HSC-T6 cells transfected by beta-catenin gene, especially when the transfected cells are stimulated by TGFbeta1. Our data suggest that beta-catenin could aggravate hepatic fibrosis induced by TGFbeta1.

Paraoxonase-1 is related to inflammation, fibrosis and PPAR delta in experimental liver disease

BACKGROUND

Paraoxonase-1 (PON1) is an antioxidant enzyme synthesized by the liver. It protects against liver impairment and attenuates the production of the pro-inflammatory monocyte chemoattractant protein-1 (MCP-1). We investigated the relationships between hepatic PON1 and MCP-1 expression in rats with liver disease and explored the possible molecular mechanisms involved.

METHODS

CCl4 was administered for up to 12 weeks to induce liver damage. Serum and hepatic levels of PON1 and MCP-1, their gene and protein expression, nuclear transcription factors, and histological and biochemical markers of liver impairment were measured.

RESULTS

High levels of PON1 and MCP-1 expression were observed at 12th week in the hepatocytes surrounding the fibrous septa and inflammatory areas. CCl4-administered rats had an increased hepatic PON1 concentration that was related to decreased gene transcription and inhibited protein degradation. Decreased PON1 gene transcription was associated with PPARdelta expression. These changes were accompanied by increased hepatic MCP-1 concentration and gene expression. There were significant direct relationships between hepatic PON1 and MCP-1 concentrations (P = 0.005) and between PON1 and the amount of activated stellate cells (P = 0.001).

CONCLUSION

Our results from this experimental model suggest a hepato-protective role for PON1 against inflammation, fibrosis and liver disease mediated by MCP-1.

Chronic High Doses of Thioacetamide Followed by Vitamin A Modify Dolichol, Dolichol Isoprenoids, and Retinol Content in Rat Liver Cells

Our line of researches follows the hypothesis that dolichol and retinol metabolism might be interrelated and involved in liver fibrosis. To this end, in this study rats were subjected to chronic treatment with thioacetamide (TAA) (300 mg/L liquid diet) for 1 and 2 months and, after liver damage had occurred, supplemented with vitamin A before sacrifice. Dolichol, dolichol isoprene units, and retinol content were determined in isolated parenchymal and sinusoidal liver cells (hepatic stellate cells; Kupffer cells; sinusoidal endothelial cells). Dolichol increased in hepatocytes after TAA treatment, with or without vitamin A. Dolichol decreased in the other cells. Retinol in general decreased. In hepatocytes, retinol decreased only on normal nutrition, while the vitamin A load was taken up normally. The percentages of dolichol isoprene units (Dol-16 to Dol-20, in rats) confirm that Dol-18, which was not modified in percentage by TAA on normal nutrition, did not increase after vitamin A, as it did in control cells (7-12%). The behavior of Dol-18 was similar in all the cells studied. Vitamin A might reveal a latent damage produced by TAA on dolichol homologues. These data support previous hypotheses that the action of TAA depends on the administration modality, the dosage, and the diet, and that Dol-18 might have different functions and compartmentalization in the cells. Furthermore, the results support the hypothesis that dolichol chain length might be interrelated with retinol metabolism, perhaps through their metabolites.

Coagulation status modulates murine hepatic fibrogenesis: implications for the development of novel therapies

BACKGROUND

There is strong evidence demonstrating that coagulation system activation contributes to wound healing and promotes organ fibrosis. Several epidemiological studies have now shown that prothrombotic status, including carriage of the factor (F)V Leiden mutation, is associated with rapid progression of hepatic fibrosis.

OBJECTIVES

To assess the effect of a procoagulant state on progression of hepatic fibrosis in a controlled environment and to test whether anticoagulation could attenuate fibrogenesis.

METHODS

We investigated the effects of coagulation status on liver fibrosis development in a mouse model of chronic toxic liver injury. Prothrombotic FV Leiden mutant mice, C57BL/6 control animals and anticoagulated mice were studied after chronic exposure to carbon tetrachloride.

RESULTS

Carriage of the FV Leiden mutation caused a significant increase in hepatic fibrosis. Anticoagulation with warfarin significantly reduced fibrosis progression in wild-type mice but was less effective against the profibrotic FV Leiden mutation. Changes in the fibrosis scores were mirrored by changes in liver hydroxyproline content and hepatic stellate cell activation detected by alpha-smooth muscle actin expression.

CONCLUSIONS

These results demonstrate that coagulation status has a strong influence on hepatic fibrogenesis. It is likely that thrombin signaling through the proteinase-activated receptor 1 (PAR(1)) receptor expressed on hepatic stellate cells is responsible for this relationship. These results represent the first reported use of anticoagulation to slow hepatic fibrogenesis and suggest a potential novel anti-fibrotic therapeutic approach for the future.

Diagnosis and measurement of liver fibrosis by MRI in bile duct ligated rats

The noninvasive evaluation of liver fibrosis is a major clinical goal in liver diseases. Our aim was to identify MRI parameters to quantify liver fibrosis in vivo in an animal model of liver fibrosis with slight inflammation. We evaluated serum hyaluronate, liver hydroxyproline, area of liver fibrosis (image analysis), and 1.5-T MRI in 10 sham rats and 24 bile duct ligated rats with different stages of liver fibrosis. Liver signal intensity (SI)/muscle SI ratio and liver relaxation times (rT) were measured on T1 and T2 weighted sequences at different echo (TE) or recovery (RT) times of MRI. Among the 66 MRI parameters tested, the highest correlation with the area of fibrosis was observed for rT2 (r=0.78, P < 0.01). The area of liver fibrosis was independently predicted by five MRI variables (adjusted R (2)=0.78, with R (2)=0.64 for rT2 and rT1). Diagnostic accuracy for liver fibrosis was 100% using two variables: liver/muscle SI ratio on T2 at 30-ms TE and liver/muscle SI ratio on T1 at 50-ms RT. We conclude that in this animal model, fibrosis could be diagnosed with an accuracy of 100% using two MRI parameters. The quantification of liver fibrosis was very accurate either with only one MRI parameter (r=0.78 for rT2) or with five parameters (r=0.90) in this cholestatic model.

[Regulatory effects of RhoGTPase on transition of liver sinusoidal capillarization: experiment with mice of schistosomal hepatic fibrosis]

OBJECTIVE

To investigate the regulatory effects of RhoGTPase on the transition of liver sinusoidal endothelial cells and the potential mechanism thereof on the sinusoidal capillarization in schistosomal hepatic fibrosis.

METHODS

Eight-eight mice underwent abdominal infection of schistosomal cercaria so as to establish liver fibrosis models. 13 weeks later the mice were divided into 5 groups: Group A (normal control group, n = 10), Group B (group of schistosomiasis, n = 24), Group C (anti-schistosoma control group, treated with biltricide), Group D (group of schistosomiasis + hydroxyfasudil, treated with hydroxyfasudil since the week 14, n = 18), and Group E (biltricide + hydroxyfasudil, treated with biltricide since week 13 and added with hydroxyfasudil since week 14, n = 18). The mice in Group A and 6 mice of Group B were killed in week 13, and 6 mice of Groups B, C, D, and E were killed in weeks 16, 19, and 21 each. The livers were taken out to undergo electron microcopy. Immunohistochemistry was used to detect the expression of p-moesin, connective tissue growth factor (CTGF), RhoA, collagen IV (Col IV), and laminin (LN) protein expressions were assessed by Western blotting, and RT-PCR was used to detect the mRNA expression of CTGF, RhoA, and ROCK II.

RESULTS

Compared with Group A, the mRNA levels of RhoA, ROCK II, and CTGF were significantly increased (all P < 0.05) and the protein expression levels of p-moesin, CTGF, RhoA, Col IV, and LN were significantly increased (all P < 0.05) in Group B. After intervention with biltricide and/or hydroxyfasudil, the CTGF mRNA expression was significantly decreased (P < 0.05) in Group E in week 16 and the protein expression levels of CTGF, Col IV, and LN were decreased (all P < 0.05) compared with other groups, and the expression of p-moesin of Group E was significantly lower than that of Group D (P < 0.05). Electron microcopy showed that the liver sinusoids of the mice in Group E was significantly better compared with the other groups, and there was no significant difference between Groups B and D.

CONCLUSION

An upregulation of RhoGTPase that contributes to increased CTGF expression and phosphorylation of moesin may induce a transition of liver sinusoidal endothelial cells in schistosomiasis.

Grape seed extract reduces oxidative stress and fibrosis in experimental biliary obstruction

BACKGROUND AND AIM

The aim of this study was to assess the protective effect of grape seed extract (GSE) against oxidative liver injury and fibrosis induced by biliary obstruction in rats.

METHODS

Wistar albino rats were divided into four groups; control (C), GSE-treated, bile duct ligated (BDL), and BDL and GSE-treated (BDL + GSE) groups. GSE was administered at a dose of 50 mg/kg a day orally for 28 days. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels were determined to assess liver function and tissue damage, respectively. Tumor necrosis factor-alpha (TNF-alpha) and antioxidant capacity (AOC) were assayed in plasma samples. Liver tissues were taken for determination of the hepatic malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Production of reactive oxidants was monitored by chemiluminescence (CL) assay.

RESULTS

Serum AST, ALT, LDH and plasma TNF-alpha were elevated in the BDL group as compared to the control group and were significantly decreased with GSE treatment. Plasma AOC and hepatic GSH level, depressed by BDL, was elevated back to the control level in the GSE-treated BDL group. Increases in tissue MDA level, MPO activity and collagen content due to BDL were also attenuated by GSE treatment. Furthermore, luminol and lucigenin CL values in the BDL group increased dramatically compared to the control and were reduced by GSE treatment.

DISCUSSION

These results suggest that GSE protects the liver from oxidative damage following bile duct ligation in rats. This effect possibly involves the inhibition of neutrophil infiltration and lipid peroxidation; thus, restoration of oxidant and antioxidant status in the tissue.

Genistein decreases liver fibrosis and cholestasis induced by prolonged biliary obstruction in the rat

Fibrosis accompanies most chronic liver disorders and is a major factor contributing to hepatic failure. Therefore, the need for an effective treatment with the aim of modifying the clinical course of this disease is evident. The aim of this work is to determine whether genistein, which has been shown to modulate the physiology and pathophysiology of liver, is able to decrease experimental liver fibrosis and cholestasis. In male Wistar rats, the common bile duct was ligated. Administration of genistein (5 microg rat-1, day-1, p.o.) began four weeks after biliary obstruction and continued for a further four weeks. The liver was used for histological and ultrastructural analysis and for collagen quantification (hydroxyproline content). The degradation of Matrigel(R) and collagen type I was determined in homogenized liver. Bilirubins and enzyme activities were measured in serum. Genistein was able to improve normal liver histology, ultrastructure, collagen content, and biochemical markers of liver damage. It also increased Matrigel(R) and collagen type I degradation. In summary, the present report shows that genistein inhibits the fibrosis and cholestasis induced by prolonged biliary obstruction in the rat. Genistein has therapeutic potential against liver fibrosis.

Erdosteine treatment attenuates oxidative stress and fibrosis in experimental biliary obstruction

Oxidative stress, in particular lipid peroxidation, induces collagen synthesis and causes fibrosis. The aim of this study was to assess the antioxidant and antifibrotic effects of erdosteine on liver fibrosis induced by biliary obstruction in rats. Liver fibrosis was induced in Wistar albino rats by bile duct ligation (BDL). Erdosteine (10 mg/kg, orally) or saline was administered for 28 days. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels were determined to assess liver functions and tissue damage, respectively. Pro-inflammatory cytokines, TNF-alpha, IL-1beta and IL-6 and antioxidant capacity (AOC) were assayed in plasma samples. Liver tissues were taken for determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Production of reactive oxidants was monitored by chemiluminescence assay. Serum AST, ALT, LDH, and plasma cytokines were elevated in the BDL group as compared to controls and were significantly decreased by erdosteine treatment. Hepatic GSH level and plasma AOC, depressed by BDL, were elevated back to control level with erdosteine treatment. Furthermore, hepatic luminol and lucigenin chemiluminescence (CL), MDA level, MPO activity and collagen content in BDL group increased dramatically compared to control and reduced by erdosteine treatment. Since erdosteine administration alleviated the BDL-induced oxidative injury of the liver and improved the hepatic functions, it seems likely that erdosteine with its antioxidant and antifibrotic properties, may be of potential therapeutic value in protecting the liver fibrosis and oxidative injury due to biliary obstruction.

[Inhibitory effect of angiotensin blockade on hepatic fibrosis in common bile duct-ligated rats]

BACKGROUNDS AND AIMS

Angiotensin receptors are found on hepatic stellate cells, which participate in hepatic fibrosis. Therefore, it is presumed that angiotensin has a role in hepatic fibrosis. The aim of this study was to evaluate the effects of angiotensin blockade on inhibition of hepatic fibrosis in cirrhotic rat model.

MATERIAL AND METHODS

Cirrhosis with portal hypertension was produced by common bile duct ligation (BDL) in the adult Sprague-Dawley rats. They were classified into 4 groups (each group n=6) as follows; G1: BDL without drug, G2: BDL+captopril 100 mg/kg/day beginning 2 weeks after BDL, G3: BDL+captopril 100 mg/kg/day, starting just after BDL, G4: BDL+losartan 10 mg/kg/day, starting just after BDL. After 4 weeks following BDL, hepatic fibrosis was histomorphologically analyzed by Batts & Ludwig score. alpha smooth muscle actin by immunohistochemical stain, hydroxyproline contents of liver tissue by spectrophotometry and expression of collagen, procollagen, and TGF-beta by real-time PCR were measured.

RESULTS

Batts & Ludwig score were 3.8, 3.0, 2.6,and 2.6 in G1, G2, G3, and G4, respectively. The expression of alpha-SMA was significantly lower in G3 and G4 than in G1; 11.9%, 10.9%, 2.6%, and 1.1% in G1, G2, G3, and G4, respectively (p<0.05). The concentration of hydroxyproline (microg/g liver tissue) was lower in G3 and G4 compared with G1 (p<0.05). Also, the administration of angiotensin blockade just after BDL significantly reduced the expression of collagen, procollagen, and TGF-beta mRNA.

CONCLUSIONS

Angiotensin blockades are effective in the prevention of hepatic fibrosis in BDL rats.

The role of food restriction on CCl4-induced cirrhosis model in rats

Effects of food restriction on susceptibility to the toxic effect of some chemicals are controversial. In order to identify an exposure model that could maximize cirrhosis and minimize mortality rate, this study aimed to evaluate the effect of food restriction on tetrachloride carbon (CCl(4))-induced cirrhosis model in rats. Fifty-three male Wistar rats received CCl(4) 0.25 ml/kg weekly intragastrically once a week. Thirty-three had 44% food restriction (group 1); 10 rats had 25% food restriction (group 2); and 10 rats received ad libitum food (group 3). After 10 weeks, the animals were sacrificed and liver sections were collected for histology. Of the 53 animals enrolled for the study, 22 (41.5%) died before completing 10-week CCl(4). Mortality rate was significantly higher in group 1 compared to other groups (p<0.05). Cirrhosis was significantly more prevalent in group 1 than in group 3 (p<0.01), but without significant difference between groups 1 and 2 (p=0.624). We concluded that food restriction is an important issue to be considered when establishing a CCl(4)-induced cirrhosis model in rats. Moreover, there is an ideal range of food intake that predisposes to liver damage without increasing mortality leading to a more effective model.

LPS exacerbates endothelin-1 induced activation of cytosolic phospholipase A2 and thromboxane A2 production from Kupffer cells of the prefibrotic rat liver

BACKGROUND/AIMS

Thromboxane A2 (TXA2) has been suggested to play a significant role in the development of portal hypertension in fibrosis, and Kupffer cell (KC) derived TXA2 has been shown to mediate the hyperresponsiveness of the portal circulation to the vasoconstrictive actions of endothelin-1 (ET-1) during endotoxemia. The aim of this study was to determine whether the double stresses of prefibrotic changes and endotoxemia additively activate KC to increase release of TXA2 in response to ET-1, resulting in elevated portal resistance.

METHODS

One week Bile duct ligation (BDL) rats and sham-operated controls were subjected to isolated liver perfusions following LPS or saline for 6h. In a separate experiment, KC were isolated from BDL or sham rats and incubated with LPS or saline for 6h before the ET-1 treatment.

RESULTS

The double stresses of early fibrosis and LPS resulted in a greater sustained increase in portal pressure in response to ET-1 in BDL rats, and this increase correlated well with the much enhanced release of TXA2 in the perfusate. Media from the cultured KC showed significantly greater TXA2 release in response to ET-1 in BDL group than those in sham group, and LPS exacerbated this effect. Protein levels of cytosolic phospholipase A2 (cPLA2), cyclooxygenase-2, and thromboxane synthase were also significantly elevated in KC from BDL rats. ET-1 produced a marked increase in cPLA2 activation as measured by the phosphorylation of cPLA2 in KC of both BDL and sham groups. LPS greatly exacerbated the activation of cPLA2.

CONCLUSIONS

The data suggest that the double stresses additively activate KC with an upregulation of the key enzymes in the TXA2 biosynthesis and release increased amount of TXA2 via the augmented activation of cPLA2 in response to ET-1, which leads to the increased portal resistance and ultimately hepatic microcirculatory dysfunction.

Partial portal vein ligation plus thioacetamide: a method to obtain a new model of cirrhosis and chronic portal hypertension in the rat

To obtain a new model of chronic portal hypertension in the rat, two classical methods to produce portal hypertension, partial portal vein ligation and the oral administration of thioacetamide (TAA), have been combined. Male Wistar rats were divided into four groups: 1 (control; n = 10), 2 [triple partial portal vein ligation (TPVL); n = 9], 3 (TAA; n = 11), and 4 (TPVL plus TAA; n = 9). After 3 months, portal pressure, types of portosystemic collateral circulation, laboratory hepatic function tests (aspartate aminotransferase, alanine aminotransferase, bilirubin, alkaline phosphatase, and gamma-glutamyl transpeptidase) and liver histology were studied. The animals belonging to group 2 (TPVL) developed extrahepatic portosystemic collateral circulation, associated with mesenteric venous vasculopathy without hepatic destructurization or portal hypertension. Animals from group 3 (TAA) developed cirrhosis and portal hypertension but not extrahepatic portosystemic collateral circulation, or mesenteric venous vasculopathy. Finally, the animals from group 4 (TPVL + TAA) developed cirrhosis, portal hypertension, portosystemic collateral circulation, and mesenteric venous vasculopathy. The association of TPVL and TAA can be used to obtain a model of chronic portal hypertension in the rat that includes all the alterations that patients with hepatic cirrhosis usually have. This could, therefore, prove to be a useful tool to study the pathophysiological mechanisms involved in these alterations.

The effect of aminoguanidine against cholestatic liver injury in rats

We investigated the protective role of aminoguanidine (AG) in rat liver injury induced by chronic biliary obstruction. Secondary biliary cirrhosis was induced by bile duct ligation for 14 days. Swiss albino rats were divided into three groups: Common bile duct ligated (CBDL) rats; Group A, CBDL rats treated with AG as Group B and simple laparotomy group known as the Sham group; Group C. Group B received 200 mg/kg of AG intraperitoneally daily throughout 14 days. The present data showed decreased gama glutamyl transferase (GGT), aspartate aminotransferase (AST), bilirubin and alanine aminotransferase (ALT) levels in the AG treated rats, when compared with CBDL rats (p < 0.05). In the AG treated rats, tissue levels of malondialdehyde (MDA) were significantly lower than that in CBDL rats (p < 0.001). Although the levels of glutathione (GSH) in AG treated rats were higher and myeloperoxidase (MPO) were lower than that in CBDL rats, the difference was not statistically significant (p > 0.05). The levels of interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) were significantly lower and although the levels of interleukin-6 (IL-6) were lower in AG treated rats than that in CBDL rats, the difference was not statistically significant. Administration of AG in the rats with biliary obstruction resulted in inhibition of ductular proliferation and portal inflammation. The present study demonstrates that intraperitoneal administration of AG in CBDL rats maintains antioxidant defenses, reduces liver oxidative and cytokine damage and ductular proliferation and portal inflammation. This effect of AG may be useful in the preservation of liver injury in cholestasis.

Influences of reactive oxygen species and nitric oxide on hepatic fibrogenesis

BACKGROUND/AIMS

This study determined the roles of NAD(P)H oxidase, which generates reactive oxygen species (ROS), and of inducible nitric oxide synthase (iNOS), which generates nitric oxide (NO) on the development of hepatic fibrosis in mice.

METHODS

Hepatic fibrosis was produced by carbon tetrachloride administered for 12 weeks in wild-type (WT) mice and in mice with knockout of either the gp91phox subunit of the NAD(P)H complex (gp91phox-/-) or of iNOS (iNOS(-/-)).

RESULTS

Liver fibrosis and hydroxyproline after carbon tetrachloride was lower in gp91phox-/- and in iNOS(-/-) mice than in WT mice. The increase in alpha2(I) collagen mRNA was absent in the gp91phox-/- but not in the iNOS(-/-) mice. Transformation growth factor beta (TGF-beta) mRNA was increased more in the gp91phox-/- than in the WT mice, while in the iNOS(-/-) mice there was no increase in TGF-beta mRNA. 3-Nitrotyrosine was similarly increased by carbon tetrachloride in gp91phox-/- and WT mice, while there was no increase in the iNOS(-/-) mice.

CONCLUSIONS

Deficiencies in NAD(P)H oxidase and in iNOS separately reduce, but do not eliminate carbon tetrachloride-induced liver fibrosis. Likely causes for this inhibitory effects are decreases in the production of ROS in NAD(P)H deficiency and of peroxinitrite radicals in iNOS deficiency.

Cholesterol-fed rabbit as a unique model of nonalcoholic, nonobese, non-insulin-resistant fatty liver disease with characteristic fibrosis

BACKGROUND

The number of patients suffering from metabolic syndrome is increasing rapidly. Metabolic syndrome causes severe pathological changes in various organs, including the liver, and its main phenotype is nonalcoholic fatty liver disease (NAFLD). NAFLD has a broad spectrum ranging from simple fatty change to severe steatohepatitis with marked fibrosis. Recently, several experimental animal models for NAFLD have been proposed. However, most were established by rather artificial conditions such as genetic alteration. In the present study, we tried to establish a unique animal model mimicking some of the physiopathological features of NAFLD using high-cholesterol-fed rabbits.

METHODS

Male rabbits fed with standard rabbit food containing 1% cholesterol for 8 weeks and 12 weeks were compared to controls (six rabbits/group). The weight of food was strictly restricted to 100 g/rabbit per day.

RESULTS

Body weights and fasting plasma insulin levels showed no significant differences among the groups. In contrast, characteristic fine fibrosis was extended from perivenular to pericellular areas, and microvesicular fatty change with ballooning degeneration was observed in perivenular areas in livers of the cholesterol-fed rabbits. Increase of serum cholesterol level, activation of hepatic stellate cells, and exposure to oxidative stress were also recognized.

CONCLUSIONS

Cholesterol-fed rabbits share several physiopathological features of NAFLD. Because this model did not show insulin resistance or obesity, it may be useful for elucidating the mechanism of NAFLD related mainly to hyperlipidemia.

Preventive and therapeutic effects of angiotensin II type 1 receptor blocker on hepatic fibrosis induced by bile duct ligation in rats

BACKGROUND

The aim of this study was to examine the preventive and therapeutic effects of an angiotensin II type 1 receptor blocker, candesartan, on cholestasis-induced liver fibrosis.

METHODS

Candesartan was administered orally for 21 days immediately after bile duct ligation to evaluate its preventive effect, and for 21 days starting 3 weeks after bile duct ligation to evaluate its therapeutic effect. Fibrosis was assessed by measuring hepatic hydroxyproline (Hyp) content. The activated hepatic stellate cells (HSCs) were assessed by alpha-smooth muscle actin (alpha-SMA) immunostaining. The gene expression of collagen I, transforming growth factor-beta1 (TGF-beta1), and connective tissue growth factor (CTGF) in the liver was examined by real-time reverse transcriptase-polymerase chain reaction.

RESULTS

As a preventive effect, candesartan reduced the hepatic Hyp content by 36%, alpha-SMA-positive cells by 65%, hepatic TGF-beta1 content by 35%, and the expression of collagen I by 72%, TGF-beta1 by 67%, and CTGF mRNA by 69%. As a therapeutic effect, candesartan reduced the hepatic Hyp content by 48%, TGF-beta1 content by 54%, and the expression of collagen I by 47%, TGF-beta1 by 43%, and CTGF mRNA by 53%. Significant decreases in lipid peroxidation markers, hepatic thiobarbituric acid-reactive substance, and 4-hydroxy-2-nonenal were observed in candesartan-treated rats.

CONCLUSIONS

Candesartan attenuated liver fibrosis via suppression of collagen I and TGF-beta1 expression, HSC activation, and lipid peroxidation protein, showing its preventive and therapeutic effects on cholestasis-induced liver fibrosis.

Inhibition of aromatase improves nutritional status following portacaval anastomosis in male rats

BACKGROUND/AIMS

The portacaval anastamosis (PCA) rat is a model of the nutritional and endocrine consequences of liver cirrhosis. We hypothesized that failure to gain body weight in the PCA rat was the consequence of low testosterone levels and will be reversed by 4-hydroxyandrostenedione, a specific aromatase inhibitor.

METHODS

Male Sprague-Dawley rats subjected to an end-to-side PCA or sham surgery were administered either 4-hydroxyandrostenedione or vehicle. Food intake, food efficiency, and body weight were measured, animals sacrificed 3 weeks after surgery, visceral organs harvested and plasma sex steroids measured. Hepatic RNA was extracted and dot blots done to quantify the expression of sex hormone dependent enzymes 16alpha hydroxylase and 15beta hydroxylase.

RESULTS

Growth, food intake, food efficiency and plasma testosterone were lower and plasma estradiol higher in PCA than sham rats. Hepatic expression of testosterone driven 16alpha hydroxylase was lower and estradiol driven 15beta hydroxylase higher in PCA rats. These alterations were reversed by 4-hydroxyandrostenedione.

CONCLUSIONS

These observations demonstrate that use of aromatase inhibitor reverses the nutritional and endocrine abnormalities in the PCA rat and suggest that this approach may be useful in cirrhotic patients.