Bile Duct Ligation Rat Model Research Articles

Hepatic stellate cell‐targeted delivery of M6P‐HSA‐glycyrrhetinic acid attenuates hepatic fibrogenesis in a bile duct ligation rat model

Hepatic stellate cells (HSCs) play a key role in fibrogenesis. Here, we used mannose-6-phosphate-modified human serum albumin (M6P(26)-HSA) as a selective carrier to deliver antifibrotic drug 18beta-glycyrrhetinic acid (18beta-GA) in experimental fibrosis animals, and tested its effect in injured liver tissues. Bile duct ligation (BDL) was performed to induce liver damage in rats. Masson's stain and immunocytochemistry were used to assess hepatic collagen deposits and uptakes of M6P(26)-HSA-GA in HSCs in rat livers. Gene expression profiles of procollagen type I alpha2, smooth muscle actin (SMA), and transforming growth factor-beta1 (TGF-beta1) were analysed by TaqMan and quantitative polymerase chain reaction assays. The depositions of M6P(26)-HSA-GA in the HSC-T6 cell line and primary HSCs were assessed by immunofluorescent staining. Treatment with M6P(26)-HSA-GA at 10 mg/kg (three times/week for 2 weeks), but not the equivalent doses of free 18beta-GA and M6P(26)-HSA carrier alone, could significantly attenuate collagen deposits in BDL rat liver. Masson's stain and TaqMan assay revealed significant modulation of procollagen type I alpha2 in the BDL-injured liver. The depositions of M6P(26)-HSA-GA in HSCs were revealed by immunostaining with HSA and SMA markers. M6P(26)-HSA bound activated HSCs in vitro and the immunoreactivity of M6P(26)-HSA-GA was detected in the cytoplasm and cell surface of HSCs and HSC-T6 cells. The gene transcript levels of SMA and TGF-beta1 were modulated in HSC-T6 cells treated with M6P(26)-HSA-GA. The M6P(26)-HSA holds promise as a targeting carrier for the liver or HSCs, which may be used to deliver 18beta-GA as a therapeutic agent to treat liver fibrosis.

A new cholestatic mouse model provides insights into renal reabsorption of sodium

A new cholestatic mouse model provides insights into renal reabsorption of sodium

Chronic bile duct obstruction induces changes in plasma and hepatic levels of cytokines and nitric oxide in the rat

Chronic bile duct ligation (BDL) is a useful model of cirrhosis. However, its parallel plasma and liver changes in levels of cytokines and nitric oxide (NO), involved in liver damage, remain unknown. The aims of this work were to quantify both the plasma and hepatic levels of five cytokines and NO in cirrhotic rats, 28 days after bile BDL, and to analyze their relationship with liver damage markers. One group of male Wistar rats was bile duct ligated and another group was sham operated, both groups were sacrificed 28 days after BDL. Plasma and liver cytokines, tumor necrosis factor- α (TNF- α), interleukin-6, -1 β, -10 (IL-6, -1 β, -10) and interferon- γ (IFN- γ), were measured by ELISA. Plasma and hepatic NO was determined as NO 2 −+NO 3 − by an enzymatic method. Alkaline phosphatase, γ-glutamyl transpeptidase, alanine aminotransferase and bilirubins were determined in plasma. Collagen, lipid peroxidation and glycogen were quantified in liver. Two histopathological staining techniques were performed. BDL-induced cirrhosis was corroborated by the elevated liver damage markers and histopathological analysis. Chronic BDL significantly increased ( P < 0.05 ) most of plasma and hepatic cytokine levels and diminished the hepatic IFN- γ amount. NO was increased in both tissues, but such change was only significant in plasma. Biliary cirrhosis produces interesting changes in plasma and hepatic levels of cytokines and NO. This finding in chronic BDL model in rats has not been previously described in both tissues for such cytokines and NO. Cytokines and NO imbalance favor establishment and perpetuation of cirrhosis.

Cholangiocyte Endothelin 1 and Transforming Growth Factor β1 Production in Rat Experimental Hepatopulmonary Syndrome

Cholangiocyte Endothelin 1 and Transforming Growth Factor β1 Production in Rat Experimental Hepatopulmonary Syndrome

Use of a mixed endothelin receptor antagonist in portopulmonary hypertension: A safe and effective therapy?

Portopulmonary hypertension (PPHTN), a severe complication of portal hypertension is observed in 3%-6% of patients evaluated for liver transplantation. Endothelin-1, a potent vasoconstrictor, is likely to play a role in the pathogenesis of primary pulmonary hypertension, and, in 2 recent trials, the dual endothelin receptor antagonist bosentan has shown beneficial effects in this disease. A role for endothelins in the development of both pulmonary hypertension and cirrhosis has been suggested. We therefore hypothesized that endothelin receptor blockade may be beneficial in the treatment of PPHTN. We report a case of a 42-year-old patient with PPHTN and alcoholic cirrhosis treated with the mixed endothelin receptor antagonist bosentan. The patient rapidly improved from NYHA IV to stage II, experienced a remarkable improvement of 6-minute walking distance from 0 to 590 m within 6 months, and resumed working full-time as a locksmith after 7 months of treatment. Improvement of cardiovascular parameters included a reduction of pulmonary vascular resistance by 60%, a decrease of mean pulmonary artery pressure (mPAP) from 55 to 44 mm Hg at 9 months, and a decline of plasma B-type natriuretic peptide (BNP) from 339 pg/mL to 19 pg/mL after 1 year. There were no adverse events except for a transient decrease in systemic blood pressure. To our knowledge, this is the first report of a patient with PPHTN treated with an endothelin receptor antagonist. The marked and sustained improvement supports the undertaking of controlled studies of the safety and efficacy of bosentan in PPHTN.

Cholestasis and failure of interferon-alpha treatment

We are grateful to Dr. Poupon for pointing out the potential involvement of cholestasis and bile salts in interferon (IFN)-α treatment failure in HCV patients. In the past few years, Dr. Poupon and his colleagues have demonstrated that cholestasis has a time-dependent inhibitory effect on 2′5′-oligoadenylate synthetase activity in the liver and spleen in a rat model of bile-duct ligation, and that physiological concentrations of bile salts can inhibit IFN-α-induced 2′5-oligoadenylate synthetase, MxA, and natural killer cell activities in cultured hepatocytes, HepG2 cells, Huh7, PLC/PRF-5, and CHO cells.1-3 These findings strongly suggest that cholestasis and bile salts may negatively modulate the efficacy of IFN-α treatment in hepatitis C virus (HCV) infection. Indeed, several studies, including one from Dr. Poupon's laboratory, show that cholestasis is a predictor of IFN-α treatment failure in HCV infection.4 However, recent clinical evidence from several studies suggests that patients with cholestatic viral hepatitis do respond to IFN-α antiviral therapy.5-8 For example, Gopal et al.reported that serum levels of HCV-RNA became undetectable in 4 of 7 cholestatic HCV patients after they received treatment with IFN-α2b and ribavirin.5 In a separate case report, a patient with acute HCV infection complicated with severe cholestasis was also successfully treated with IFN-α.8 Although treatment may not prevent progressive graft failure, combined IFN-α/ribavirin therapy appeared to inhibit HCV replication in severe recurrent cholestatic hepatitis C after transplantation.6 The success of IFN-α therapy in these patients may reflect findings from animal experiments, which have shown that IFN-α2b has antifibrotic and anticholestatic effects in a rat model of bile-duct ligation.9 Therefore, although we fully agree with Dr. Poupon that bile salts attenuate innate and acquired immunity as well as IFN-α signaling in the liver, we believe that observations of the effect of IFN-α treatment in cholestatic HCV infection are inconclusive. Further clinical studies are required to determine whether IFN-α treatment is effective in cholestatic HCV infection. Bin Gao M.D., Ph.D.*, Feng Hong M.D.*, Svetlana Radaeva Ph.D.*, * Section on Liver Biology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD.

Peribiliary myofibroblasts in biliary type liver fibrosis

Biliary type liver fibrosis develops as part of the wound healing response to bile duct injury in chronic cholestatic liver diseases. The origin of myofibroblasts accumulating together with extracellular matrix around proliferating bile duct structures (referred to as ductular reaction) in the setting of cholestatic injury, has been investigated mostly in the rat bile duct ligation model. Evidence indicates that hepatic stellate cells undergo a myofibroblastic transition following bile duct ligation and that myofibroblastic hepatic stellate cells disclose chemoattraction towards bile duct structures in cholestatic liver. On the basis of morphological studies, nevertheless, the origin of peribiliary myofibroblasts has also been attributed to the activation and proliferation of portal fibroblasts. Bile duct epithelial cells of the ductular reaction actively contribute to the promotion and regulation of biliary type liver fibrogenesis. They synthesize and release a number of paracrine mediators such as transforming growth factor-beta, connective tissue growth factor, platelet-derived growth factor-BB, and endothelin-1 that target different liver cell types, including hepatic stellate cells and portal fibroblasts. Through these interactions, bile duct epithelial cells and peribiliary myofibroblasts cause periportal fibrosis in cholestatic and also probably other types of liver diseases.

Peribiliary myofibroblasts in biliary type liver fibrosis

Biliary type liver fibrosis develops as part of the wound healing response to bile duct injury in chronic cholestatic liver diseases. The origin of myofibroblasts accumulating together with extracellular matrix around proliferating bile duct structures (referred to as ductular reaction) in the setting of cholestatic injury, has been investigated mostly in the rat bile duct ligation model. Evidence indicates that hepatic stellate cells undergo a myofibroblastic transition following bile duct ligation and that myofibroblastic hepatic stellate cells disclose chemoattraction towards bile duct structures in cholestatic liver. On the basis of morphological studies, nevertheless, the origin of peribiliary myofibroblasts has also been attributed to the activation and proliferation of portal fibroblasts. Bile duct epithelial cells of the ductular reaction actively contribute to the promotion and regulation of biliary type liver fibrogenesis. They synthesize and release a number of paracrine mediators such as transforming growth factor-beta, connective tissue growth factor, platelet-derived growth factor-BB, and endothelin-1 that target different liver cell types, including hepatic stellate cells and portal fibroblasts. Through these interactions, bile duct epithelial cells and peribiliary myofibroblasts cause periportal fibrosis in cholestatic and also probably other types of liver diseases.

Angiotensin-Converting Enzyme Inhibition Attenuates the Progression of Rat Hepatic Fibrosis

Background & Aims: There is a significant relationship between inheritance of high transforming growth factor (TGF)-β1 and angiotensinogen-producing genotypes and the development of progressive hepatic fibrosis in patients with chronic hepatitis C. In cardiac and renal fibrosis, TGF-β1 production may be enhanced by angiotensin II, the principal effector molecule of the renin-angiotensin system. The aim of the present study was to determine the effects of the angiotensin-converting enzyme inhibitor, captopril, on the progression of hepatic fibrosis in the rat bile duct ligation model. Methods: Rats were treated with captopril (100 mg · kg −1 · day −1) commencing 1 or 2 weeks after bile duct ligation. Animals with bile duct ligation only and sham-operated animals served as controls. Four weeks after bile duct ligation, indices of fibrosis were assessed. Results: Captopril treatment significantly reduced hepatic hydroxyproline levels, mean fibrosis score, steady state messenger RNA levels of TGF-β1 and procollagen α1(I), and matrix metalloproteinase 2 and 9 activity. Conclusions: Captopril significantly attenuates the progression of hepatic fibrosis in the rat bile duct ligation model, and its effectiveness should be studied in human chronic liver diseases associated with progressive fibrosis.

Haemodynamic and renal evolution of the bile duct-ligated rat

In the present study we have characterized the evolution of changes in systemic haemodynamics (thermodilution in conscious animals) and sodium balance (metabolic cages) in a model of liver cirrhosis induced by chronic bile duct ligation (BDL). Mean arterial pressure (BDL, 111.5+/-4.7 mmHg; sham-operated, 122.9+/-3.0 mmHg) and peripheral vascular resistance (BDL, 2.63+/-0.08 units; sham-operated, 2.93+/-0.09 units) were lower in BDL rats from day 12 after surgery and decreased progressively throughout the following days. Portal hypertension was evident earlier in BDL rats and was maintained throughout the study period. Cardiac index (BDL, 58.8+/-3. 9 ml.min(-1).100 g(-1); sham-operated, 43.9+/-1.5 ml.min(-1).100 g(-1)) and stroke volume (BDL, 147.2+/-12.7 ml.beat(-1).100 g(-1); sham-operated, 109.0+/-4.2 ml.beat(-1).100 g(-1)) were significantly elevated in the BDL rats only from day 18 after surgery. There were no significant differences in sodium balance between the groups until day 16 after surgery, at which time BDL animals started to retain significantly more sodium than the controls. Sodium retention increased progressively, and at day 20 BDL rats had retained 0.7 mmol/100 g more than the control animals (accumulated retention: BDL, 2.2+/-0.2 mmol/100 g; sham-operated, 1.5+/-0.2 mmol/100 g). Plasma renin activity and aldosterone concentration were not elevated in the BDL animals at days 12, 16 or 20 after surgery. These data indicate that the BDL rat model shows early portal hypertension, peripheral vasodilation and arterial hypotension, several days before sodium retention is detectable, and in the absence of changes in plasma levels of renin and aldosterone. Overall, these data suggest that, in the BDL rat model, sodium retention is secondary to portal hypertension and peripheral vasodilation.

Endothelin-1 in the rat bile duct ligation model of hepatopulmonary syndrome: correlation with pulmonary dysfunction

Background/Aims: Models of hepatopulmonary syndrome require both hepatic injury and portal hypertension to develop pulmonary microvascular and gas exchange abnormalities. Recently, increased endothelin-1 levels associated with vasodilatation, have been observed in cirrhosis. We investigated endothelin-1 production in common bile duct ligated animals with hepatopulmonary syndrome in comparison to partial portal vein ligated animals that do not develop hepatopulmonary syndrome. Methods: Organ and plasma endothelin-1 were measured in sham, bile duct ligated and portal vein ligated rats, and Northern analysis and immunohistochemistry were performed in liver. Plasma endothelin-1 levels were correlated with pulmonary endothelial nitric oxide synthase levels and alveolar-arterial oxygen gradients. Results: Hepatic and plasma endothelin-1 increased only after bile duct ligation, and were accompanied by increased hepatic endothelin-1 mRNA and increased endothelin-1 protein in biliary epithelium. Plasma endothelin-1 levels correlated directly with both pulmonary endothelial nitric oxide synthase levels and alveolar-arterial gradients. Conclusions: Enhanced hepatic production and increased plasma levels of endothelin-1 occur after bile duct ligation, but not after portal vein ligation, and correlate with associated molecular and gas exchange alterations in the lung. Endothelin-1 may contribute to the pathogenesis of hepatopulmonary syndrome.

Mechanisms of hepatic fibrosis.

Mechanisms of hepatic fibrosis.

Sequential increases in the intrahepatic expression of epidermal growth factor, basic fibroblast growth factor, and transforming growth factor beta in a bile duct ligated rat model of cirrhosis.

Chronic hepatic regeneration constitutes an important part of the cirrhotic process. The factors regulating chronic hepatic regeneration, however, remain unclear. We therefore analyzed the intrahepatic messenger RNA (mRNA) expression of growth factors (epidermal growth factor [EGF], basic fibroblast growth factor [bFGF], hepatocyte growth factor [HGF], transforming growth factor [TGF]-alpha, and TGF-beta) at progressive time points (postoperative days 2, 7, 14, and 21) in a rat bile duct-ligated (BDL) model of cirrhosis versus sham controls. Intrahepatic growth factor mRNA expression was quantitatively assessed by polymerase chain reaction (PCR) using a dot-blot hybridization technique. Cirrhosis was associated with statistically significant (P < .05) progressive increases in the intrahepatic mRNA expression of bFGF (80-fold), EGF (25-fold), and TGF-beta (fourfold) in BDL animals versus controls. Furthermore, immunohistochemistry of hepatic sections showed a progressive up-regulation of bFGF protein in areas of bile duct proliferation. These areas also showed a dramatic increase in the number of hepatic stellate cells (HSC). In contrast, the intrahepatic expression of hepatocyte growth factor (HGF) mRNA was only significantly increased at postoperative days 7 and 14 in BDL animals before returning to control levels as cirrhosis developed. There were no significant differences found at any timepoint in the expression of TGF-alpha in BDL animals versus controls. In conclusion, the development of cirrhosis in this BDL rat model was associated with a progressive increase in the intrahepatic expression of EGF, bFGF, and TGF-beta. Early increased expression of HGF was not maintained in established cirrhosis. The findings suggest that these growth factors may play important roles in the pathogenesis of chronic hepatic regeneration in cirrhosis.

Sequential increases in the intrahepatic expression of epidermal growth factor, basic fibroblast growth factor, and transforming growth factor beta in a bile duct ligated rat model of cirrhosis

Chronic hepatic regeneration constitutes an important part of the cirrhotic process. The factors regulating chronic hepatic regeneration, however, remain unclear. We therefore analyzed the intrahepatic messenger RNA (mRNA) expression of growth factors (epidermal growth factor [EGF], basic fibroblast growth factor [bFGF], hepatocyte growth factor [HGF], transforming growth factor [TGF]-alpha, and TGF-beta) at progressive time points (postoperative days 2, 7, 14, and 21) in a rat bile duct-ligated (BDL) model of cirrhosis versus sham controls. Intrahepatic growth factor mRNA expression was quantitatively assessed by polymerase chain reaction (PCR) using a dot-blot hybridization technique. Cirrhosis was associated with statistically significant (P < .05) progressive increases in the intrahepatic mRNA expression of bFGF (80-fold), EGF (25-fold), and TGF-beta (fourfold) in BDL animals versus controls. Furthermore, immunohistochemistry of hepatic sections showed a progressive up-regulation of bFGF protein in areas of bile duct proliferation. These areas also showed a dramatic increase in the number of hepatic stellate cells (HSC). In contrast, the intrahepatic expression of hepatocyte growth factor (HGF) mRNA was only significantly increased at postoperative days 7 and 14 in BDL animals before returning to control levels as cirrhosis developed. There were no significant differences found at any timepoint in the expression of TGF-alpha in BDL animals versus controls. In conclusion, the development of cirrhosis in this BDL rat model was associated with a progressive increase in the intrahepatic expression of EGF, bFGF, and TGF-beta. Early increased expression of HGF was not maintained in established cirrhosis. The findings suggest that these growth factors may play important roles in the pathogenesis of chronic hepatic regeneration in cirrhosis. (Hepatology 1997 Sep;26(3):624-33)

Effect of pentoxifylline in rat and swine models of hepatic fibrosis: role of fibroproliferation in its mechanism

Fibroproliferation was studied in two animal models of liver disease. Oral feeding of yellow phosphorus to pigs reproducibly results in fibrosis after 8 weeks of feeding, extensive fibrosis after 12 weeks and cirrhosis after 16 weeks of yellow phosphorus. Bile duct ligation was used to induce cirrhosis in the rat. Fibroproliferation was assessed as uptake of tritiated thymidine into fibroblasts which had been incubated with monocyte-conditioned medium obtained from monocytes of pigs treated with yellow phosphorus or bile duct-ligated rats and compared to the corresponding controls. Fibrosis was assessed by collagen content of liver sections obtained from the two animal models. The collagen content was determined by quantitation of Sirius red/Fast green-stained liver sections. In both animal models collagen content was significantly elevated at the conclusion of the treatment. Collagen content of liver sections of yellow phosphorus-treated animals were elevated (40 ± 2.7, n = 15) compared to mineral oil-treated controls (23 ± 1.2, n = 12) and collagen levels in the bile duct-ligated rat model liver sections were elevated (31.2 ± 1.6, n = 6) compared to sham-operated controls (21.6 ± 0.7, n = 6). The results of the fibroproliferation assay indicate that monocytes obtained from pigs treated with yellow phosphorus produce fibroproliferative factors during the development of fibrosis. This is in contrast to the bile duct-ligated rat model where no differences were observed in the production of fibroproliferative factors in the bile duct-ligated rats compared to sham operated controls suggesting that this may not be a key event in this model of fibrosis. Pentoxifylline treatment of the yellow phosphorus induced swine model of hepatic fibrosis has been associated with a marked improvement in fibrosis. In this study treatment of fibrotic pigs with pentoxifylline was associated with an improvement in liver function tests, a reduction of collagen content of liver sections, and reduction in fibroproliferation in pigs receiving yellow phosphorus treatment. Fibroproliferative factors were produced during the development of fibrosis in the swine model of fibrosis and their effect was blocked by pentoxifylline administered in vivo. This is in contrast to the bile duct-ligated rat model where pentoxifylline treatment was not associated with improvement in liver function tests or reduction of collagen content of liver sections and did not alter the fibroproliferative activity of monocyte-conditioned media. Taken together these results suggest that fibroproliferation and increased synthesis of collagen are key events in the yellow phosphorus-induced pig model of hepatic fibrosis and that the action of pentoxifylline in this animal model is likely to be related to its effects on fibroproliferation with a subsequent effect on collagen production. This is in contrast to the bile duct-ligated rat model where the results from this study suggest that fibroproliferation per se does not appear to be a key event and where pentoxifylline treatment does not alter fibroproliferative activity nor alter the course of fibrosis in this animal model.

Xanthine oxidase inhibition reduces cholestatic liver injury in the bile duct-ligated rat model without affecting hepatocyte lipid peroxidation: [formula omitted] Ped. Liver Ctr., Hepatobiliary Research Ctr., Dept. of Pediatrics, Univ. of Colorado School of Medicine and The Children's Hosp., Denver, CO

Xanthine oxidase inhibition reduces cholestatic liver injury in the bile duct-ligated rat model without affecting hepatocyte lipid peroxidation: [formula omitted] Ped. Liver Ctr., Hepatobiliary Research Ctr., Dept. of Pediatrics, Univ. of Colorado School of Medicine and The Children's Hosp., Denver, CO

Effects of bile duct ligation on calcium excretion in the rat†

In an earlier study we showed that bile duct-ligated rats were highly susceptible to gentamicin nephrotoxicity and that oral calcium administration had a pronounced protective effect. The mechanism by which this occurs is unclear. Because cations compete with gentamicin for tubule binding sites, it has been suggested that the increased susceptibility of the kidney to gentamicin after bile duct ligation might result from decreased cation excretion. The aim of this study was to determine the effect of bile duct ligation on calcium excretion in relation to overall renal function. Male Sprague-Dawley rats underwent bile duct ligation and division. Pair-fed sham-operated rats served as controls. Metabolic and clearance studies were carried out at 3, 5, 7, 14 and 21 days after surgery. Urine output was higher in bile duct-ligated rats, and they excreted more calcium at 3, 5, 7 and 14 days, while excreting less sodium than controls. We conclude that after bile duct ligation, there is increased calcium excretion, which is independent of the abnormality in sodium excretion. Enhanced nephrotoxicity with aminoglycosides in the bile duct-ligated rat model cannot be explained by decreased calcium excretion.