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)-beta1 and angiotensinogen-producing genotypes and the development of progressive hepatic fibrosis in patients with chronic hepatitis C. In cardiac and renal fibrosis, TGF-beta1 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 sewed as controls. Four weeks after bile duct ligation, indices of fibrosis were assessed. Results: Cap topril treatment significantly reduced hepatic hydroxyproline levels, mean fibrosis score, steady state messenger RNA levels of TGF-beta1 and procollagen alpha1(I), and matrix metalloproteinase 2 and 9 activity. Conclusions: Captopril significantly attenuates the progression of hepatic fibrosis in the vat bile duct ligation model, and its effectiveness should be studied in human chronic liver diseases associated with progressive fibrosis.

Cholestasis in a murine experimental model: lesions include hepatocyte ischemic necrosis

OBJECTIVE: To establish a murine experimental model of bile duct obstruction that would enable controlled observations of the acute and subacute phases of cholestasis. METHODOLOGY: Adult male isogenic BALB/c mice underwent a bile duct ligation (22 animals) or a sham operation (10 animals). Fifteen days after surgery, or immediately after the animal's death, macroscopic findings were noted and histological study of the liver, biliary tree, and pancreas was performed (hematoxylin-eosin and Masson trichromic staining). RESULTS: Beginning 24 hours after surgery, all animals from the bile duct ligation group presented progressive generalized malaise. All animals presented jaundice in the parietal and visceral peritoneum, turgid and enlarged liver, and accentuated dilatation of gallbladder and common bile duct. Microscopic findings included marked dilatation and proliferation of bile ducts with accentuated collagen deposits, frequent areas of ischemic necrosis, hepatic microabscesses, and purulent cholangitis. Animals from the sham operation group presented no alterations. CONCLUSION: We established a murine experimental model of induced cholestasis, which made it possible to study acute and subacute tissue lesions. Our data suggests that in cholestasis, hepatic functional ischemia plays an important role in inducing hepatic lesions, and it also suggests that the infectious process is an important factor in morbidity and mortality.

Angiogenesis and experimental hepatic fibrosis

Angiogenesis is a basic change occurring during repair by granulation tissue. This process seems to precede fibrosis formation in most types of chronic liver disease. To examine its presence and significance in different types of hepatic insults, this paper sought to identify the presence, evolution and peculiarities of angiogenesis in the most common experimental models of hepatic fibrosis. The characterization of cells, vessels and extracellular matrix and the identification of factors associated with endothelium (factor VIII RA), vascular basement membrane, other components of the vascular walls (actin, elastin) and the presence of the vascular-endothelial growth factor were investigated. The models examined included Capillaria hepatica septal fibrosis, whole pig serum injections, carbon tetrachloride administration, main bile duct ligation and Schistosoma mansoni infection. The first four models were performed in rats, while the last used mice. All models studied exhibited prominent angiogenesis. The most evident relationship between angiogenesis and fibrosis occurred with the C. hepatica model due to circumstances to be discussed. Special attention was paid to the presence of pericytes and to their tendency to become detached from the vascular wall and be transformed into myofibroblasts, which is a sequence of events that explains the decisive role angiogenesis plays in fibrosis.

Poly (ADP-ribose) polymerase-1 is a key mediator of liver inflammation and fibrosis.

Poly (ADP-ribose) polymerase 1 (PARP-1) is a constitutive enzyme, the major isoform of the PARP family, which is involved in the regulation of DNA repair, cell death, metabolism, and inflammatory responses. Pharmacological inhibitors of PARP provide significant therapeutic benefits in various preclinical disease models associated with tissue injury and inflammation. However, our understanding the role of PARP activation in the pathophysiology of liver inflammation and fibrosis is limited. In this study we investigated the role of PARP-1 in liver inflammation and fibrosis using acute and chronic models of carbon tetrachloride (CCl4 )-induced liver injury and fibrosis, a model of bile duct ligation (BDL)-induced hepatic fibrosis in vivo, and isolated liver-derived cells ex vivo. Pharmacological inhibition of PARP with structurally distinct inhibitors or genetic deletion of PARP-1 markedly attenuated CCl4 -induced hepatocyte death, inflammation, and fibrosis. Interestingly, the chronic CCl4 -induced liver injury was also characterized by mitochondrial dysfunction and dysregulation of numerous genes involved in metabolism. Most of these pathological changes were attenuated by PARP inhibitors. PARP inhibition not only prevented CCl4 -induced chronic liver inflammation and fibrosis, but was also able to reverse these pathological processes. PARP inhibitors also attenuated the development of BDL-induced hepatic fibrosis in mice. In liver biopsies of subjects with alcoholic or hepatitis B-induced cirrhosis, increased nitrative stress and PARP activation was noted. CONCLUSION: The reactive oxygen/nitrogen species-PARP pathway plays a pathogenetic role in the development of liver inflammation, metabolism, and fibrosis. PARP inhibitors are currently in clinical trials for oncological indications, and the current results indicate that liver inflammation and liver fibrosis may be additional clinical indications where PARP inhibition may be of translational potential.

ENaC activity in collecting ducts modulates NCC in cirrhotic mice.

Cirrhosis is a frequent and severe disease, complicated by renal sodium retention leading to ascites and oedema. A better understanding of the complex mechanisms responsible for renal sodium handling could improve clinical management of sodium retention. Our aim was to determine the importance of the amiloride-sensitive epithelial sodium channel (ENaC) in collecting ducts in compensate and decompensate cirrhosis. Bile duct ligation was performed in control mice (CTL) and collecting duct-specific αENaC knockout (KO) mice, and ascites development, aldosterone plasma concentration, urinary sodium/potassium ratio and sodium transporter expression were compared. Disruption of ENaC in collecting ducts (CDs) did not alter ascites development, urinary sodium/potassium ratio, plasma aldosterone concentrations or Na,K-ATPase abundance in CCDs. Total αENaC abundance in whole kidney increased in cirrhotic mice of both genotypes and cleaved forms of α and γ ENaC increased only in ascitic mice of both genotypes. The sodium chloride cotransporter (NCC) abundance was lower in non-ascitic KO, compared to non-ascitic CTL, and increased when ascites appeared. In ascitic mice, the lack of αENaC in CDs induced an upregulation of total ENaC and NCC and correlated with the cleavage of ENaC subunits. This revealed compensatory mechanisms which could also take place when treating the patients with diuretics. These compensatory mechanisms should be considered for future development of therapeutic strategies.

Terutroban, A TP-receptor antagonist, reduces portal pressure in cirrhotic rats.

Increased production of vasoconstrictive prostanoids, such as thromboxane A2 (TXA2 ), contributes to endothelial dysfunction and increased hepatic vascular tone in cirrhosis. TXA2 induces vasoconstriction by way of activation of the thromboxane-A2 /prostaglandin-endoperoxide (TP) receptor. This study investigated whether terutroban, a specific TP receptor blocker, decreases hepatic vascular tone and portal pressure in rats with cirrhosis due to carbon tetrachloride (CCl4 ) or bile duct ligation (BDL). Hepatic and systemic hemodynamics, endothelial dysfunction, liver fibrosis, hepatic Rho-kinase activity (a marker of hepatic stellate cell contraction), and the endothelial nitric oxide synthase (eNOS) signaling pathway were measured in CCl4 and BDL cirrhotic rats treated with terutroban (30 mg/kg/day) or its vehicle for 2 weeks. Terutroban reduced portal pressure in both models without producing significant changes in portal blood flow, suggesting a reduction in hepatic vascular resistance. Terutroban did not significantly change arterial pressure in CCl4 -cirrhotic rats but decreased it significantly in BDL-cirrhotic rats. In livers from CCl4 and BDL-cirrhotic terutroban-treated rats, endothelial dysfunction was improved and Rho-kinase activity was significantly reduced. In CCl4 -cirrhotic rats, terutroban reduced liver fibrosis and decreased alpha smooth muscle actin (α-SMA), collagen-I, and transforming growth factor beta messenger RNA (mRNA) expression without significant changes in the eNOS pathway. In contrast, no change in liver fibrosis was observed in BDL-cirrhotic rats but an increase in the eNOS pathway. CONCLUSION: Our data indicate that TP-receptor blockade with terutroban decreases portal pressure in cirrhosis. This effect is due to decreased hepatic resistance, which in CCl4 -cirrhotic rats was linked to decreased hepatic fibrosis, but not in BDL rats, in which the main mediator appeared to be an enhanced eNOS-dependent vasodilatation, which was not liver-selective, as it was associated with decreased arterial pressure. The potential use of terutroban for portal hypertension requires further investigation.

Influence of distal ileum exclusion on hepatic and renal functions in presence of extrahepatic cholestasis

OBJECTIVE: To verify whether the ileal exclusion interferes with liver and kidney functional changes secondary to extrahepatic cholestasis.METHODS: We studied 24 rats, divided into three groups with eight individuals each: Group 1 (control), Group 2 (ligation of the hepatic duct combined with internal biliary drainage), and Group 3 (bile duct ligation combined with internal biliary drainage and exclusion of the terminal ileum). Animals in Group 1 (control) underwent sham laparotomy. The animals of groups 2 and 3 underwent ligation and section of the hepatic duct and were kept in cholestasis for four weeks. Next, they underwent an internal biliary bypass. In Group 3, besides the biliary-enteric bypass, we associated the exclusion of the last ten centimeters of the terminal ileum and carried out an ileocolic anastomosis. After four weeks of monitoring, blood was collected from all animals of the three groups for liver and kidney biochemical evaluation (albumin, ALT, AST, direct and indirect bilirubin, alkaline phosphatase, cGT, creatinine and urea).RESULTS: there were increased values of ALT, AST, direct bilirubin, cGT, creatinine and urea in rats from Group 3 (p < 0.05).CONCLUSION: ileal exclusion worsened liver and kidney functions in the murine model of extrahepatic cholestasis, being disadvantageous as therapeutic procedure for cholestatic disorders.

Genetic potential for an acute inflammatory response in IgA glomerulonephritis in mice

Mice selected on the basis of an acute inflammatory response (AIR) can provide information about the immunopathological mechanisms of glomerulonephritis. We studied the differences between mice selected for a maximal AIR (AIRmax that attract more polymorphonuclear cells to the site of injury) or a minimal AIR (AIRmin that attract more mononuclear cells) in an experimental model of IgA nephropathy in order to investigate the effect of genetic background on glomerular disease progression and the participation of the monocyte chemoattractant protein-1 (MCP-1) chemokine. IgA nephropathy was induced by intraperitoneal ovalbumin injection and bile duct ligation in AIRmax and AIRmin mice. Histological changes, urinary protein/creatinine ratio, serum IgA levels, immunofluorescence for IgA, IgG and complement C3 fraction, immunohistochemistry for macrophages and MCP-1, and MCP-1 levels in macerated kidney were determined. Mesangial IgA deposition was seen only in AIRmin mice, which presented more renal lesions. Increased serum IgA levels (1.5 ± 0.4 vs 0.3 ± 0.1 mg/mL, P < 0.001), high glomerular MCP-1 expression and decreased monocyte/macrophage infiltration in the interstitial area (0.3 ± 0.3 vs 1.1 ± 0.9 macrophages/field, P < 0.05) were detected in AIRmin mice compared to AIRmax mice. No glomerular monocyte/macrophage infiltration was detected in either strain. In spite of the absence of IgA deposition, AIRmax mice presented discrete or absent mesangial proliferation. The study showed that there are differences between mice selected for AIRmax and AIRmin with respect to serum IgA levels, histological damage and MCP-1 chemokine production after ovalbumin injection in combination with bile duct ligation.

Le rôle du stress oxydatif/nitrosatif dans la pathogénèse de l’encéphalopathie hépatique chronique

L'encéphalopathie hépatique (EH) est un syndrome neuropsychiatrique dû à une dysfonction hépatique où l'ammoniaque est un facteur central. Il a déjà été rapporté que l’intoxication aiguë d'ammoniaque induise le stress oxydatif/nitrosatif. La présente étude cible à évaluer le rôle du stress oxydatif/nitrosatif dans 2 modèles de l’EH chronique : (1) l’anastomose portocave (PCA) et (2) la ligation de la voie biliaire (BDL). Ces 2 modèles sont caractérisés par une hyperammoniémie et une augmentation d’ammoniaque centrale, cependant l’œdème cérébral est trouvé seulement chez les rats BDL. Des marqueurs du stress oxydatif/nitrosatif ont été évaluées dans le plasma et cortex frontal. Un stress nitrosatif central a été observé chez les rats PCA; tandis qu’un stress oxydatif/nitrosatif systémique a été démontré seulement chez les rats BDL. Ces résultats suggèrent (1) que l’hyperammoniémie chronique n’induise pas le stress oxydatif/nitrosatif systémique et (2) qu’un synergisme existe entre l’ammoniaque et le stress oxydatif/nitrosatif, en association avec l’œdème cérébral.

Le rôle de la barrière hémato-encéphalique dans la pathogénèse de l'oedème chez des rats souffrant d'insuffisance hépatique chronique

L’œdème cérébral est une complication associée à l’encéphalopathie hépatique (EH) lors d’une insuffisance hépatique chronique (cirrhose du foie). Présentement, l’origine de sa pathogenèse, vasogénique (rupture de la barrière hémato-encéphalique (BHE)) ou cytotoxique (prise anormale d’ions), n’a pas encore été déterminée. Il a été démontré que le co-transporteur Na-K-Cl (NKCC1) du côté luminal des microvaisseaux sanguins cérébraux (CMV) joue un rôle dans le développement de l’œdème cérébral dans des modèles d’ischémie où la bumetanide, un inhibiteur de NKCC, atténue l’œdème cérébral. Deux modèles d’EH ont été utilisés pour cette étude i) la ligature de la voie biliaire (BDL) qui présente l’hyperammoniémie chronique, l’œdème cérébral et le stress oxydatif systémique ; ii) l’anastomose portocave (PCA) qui présente de l’hyperammoniémie chronique seulement. Les buts du projet étaient de: i) définir l’origine du développement de l’œdème chez les rats BDL en étudiant l’extravasation de macromolécules, les jonctions serrées et l’activation des métalloprotéinases matricielles de la BHE; ii) observer les effets de l’hyperammoniémie chronique indépendamment sur la BHE chez les rats PCA; iii) évaluer le rôle de l’hyperammoniémie et du stress oxydatif et iv) étudier le rôle du NKCC1 dans les CMV dans la pathogenèse de l’œdème cérébral. Les résultats du projet démontrent que l’œdème est d’origine cytotoxique chez les rats BDL et que l’intégrité de la BHE est conservée chez les rats PCA malgré l’hyperammoniémie. L’expression génique du NKCC1 est associée à l’œdème mais pas son expression protéique et sa phosphorylation. Enfin, l’étude démontre que l’hyperammoniémie et le stress oxydatif indépendant ne jouent pas un rôle dans la pathogenèse de l’œdème mais suggère qu’ils y aient un effet synergique.

Systemic oxidative stress is implicated in the pathogenesis of brain edema in rats with chronic liver failure.

Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE); however, a correlation between blood ammonia levels and HE severity remains controversial. It is believed oxidative stress plays a role in modulating the effects of hyperammonemia. This study aimed to determine the relationship between chronic hyperammonemia, oxidative stress, and brain edema (BE) in two rat models of HE: portacaval anastomosis (PCA) and bile-duct ligation (BDL). Ammonia and reactive oxygen species (ROS) levels, BE, oxidant and antioxidant enzyme activities, as well as lipid peroxidation were assessed both systemically and centrally in these two different animal models. Then, the effects of allopurinol (xanthine oxidase inhibitor, 100mg/kg for 10days) on ROS and BE and the temporal resolution of ammonia, ROS, and BE were evaluated only in BDL rats. Similar arterial and cerebrospinal fluid ammonia levels were found in PCA and BDL rats, both significantly higher compared to their respective sham-operated controls (p<0.05). BE was detected in BDL rats (p<0.05) but not in PCA rats. Evidence of oxidative stress was found systemically but not centrally in BDL rats: increased levels of ROS, increased activity of xanthine oxidase (oxidant enzyme), enhanced oxidative modifications on lipids, as well as decreased antioxidant defense. In PCA rats, a preserved oxidant/antioxidant balance was demonstrated. Treatment with allopurinol in BDL rats attenuated both ROS and BE, suggesting systemic oxidative stress is implicated in the pathogenesis of BE. Analysis of ROS and ammonia temporal resolution in the plasma of BDL rats suggests systemic oxidative stress might be an important "first hit", which, followed by increases in ammonia, leads to BE in chronic liver failure. In conclusion, chronic hyperammonemia and oxidative stress in combination lead to the onset of BE in rats with chronic liver failure.

Pathogenèse de l’oedème cérébral dans l’encéphalopathie hépatique minimale : rôles du stress oxydatif et du lactate

L’encéphalopathie hépatique (EH) est un syndrome neuropsychiatrique découlant des complications de l'insuffisance hépatique. Les patients souffrant d'une insuffisance hépatique chronique (IHC) présentent fréquemment une EH minimale (EHM) caractérisée par des dysfonctions cognitives subtiles qui affectent leur qualité de vie. L'insuffisance hépatique entraîne une hyperammoniémie, le facteur central dans la pathogenèse de l'EH. Pourtant, les taux d'ammoniaque sérique ne sont pas corrélés avec la sévérité de l'EH lors d'une IHC, suggérant que d'autres facteurs y contribuent. L'oedème cérébral est une caractéristique neuropathologique décrite chez les patients souffrant d'une EHM et plusieurs facteurs dont le stress oxydatif, les altérations du métabolisme énergétique et l'augmentation de la glutamine cérébrale pourraient contribuer à la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC. Les mécanismes sous-jacents exacts ainsi que les relations entre ces facteurs et l'ammoniaque ne sont pas connus. Présentement, le seul traitement efficace de l'IHC est la transplantation hépatique, une option thérapeutique très limitée. Le but de cette thèse est de contribuer à l'avancement des connaissances sur les mécanismes sous-jacents liés au rôle du stress oxydatif, de la glutamine et du lactate dans la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC afin d'envisager de nouvelles options thérapeutiques. Les objectifs précis étaient: 1. Établir le rôle de l’ammoniaque et sa relation avec le stress oxydatif dans la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC. 2. Établir le rôle du stress oxydatif dans la pathogenèse de l'oedème cérébral, sa relation avec l'ammoniaque et l'effet du traitement avec des antioxydants. 3. Confirmer l'effet synergique entre l'ammoniaque et le stress oxydatif dans la pathogenèse de l'oedème cérébral. 4. Établir le rôle du lactate et de la glutamine dans la pathogenèse de l'oedème cérébral et leur relation avec l’ammoniaque. Pour atteindre ces objectifs, 2 modèles animaux d'EHM obtenus par microchirurgie chez le rat ont été utilisés: 1) la ligature de voie biliaire, un modèle d'IHC et 2) l'anastomose porto-cave, un modèle d'hyperammoniémie induite par la dérivation portosystémique. Nos résultats démontrent que l'ammoniaque et le stress oxydatif indépendamment n'induisent pas l'oedème cérébral lors d'une EHM. Pourtant, lorsque les 2 facteurs agissent ensemble ils présentent ii un effet synergique qui entraîne le développement de l'oedème cérébral, le stress oxydatif étant une première insulte, qui est suivie par l'hyperammoniémie comme deuxième insulte. En plus, le stress oxydatif a été mis en évidence seulement au niveau systémique, et non au niveau central dans notre modèle d'IHC en association avec l'oedème cérébral, suggérant que le stress oxydatif systémique est une conséquence de la dysfonction hépatique et que l'hyperammoniémie n’induit pas le stress oxydatif ni systémique ni central. Nous avons démontré qu’une augmentation du lactate cérébral est une conséquence directe de l'hyperammoniémie et joue un rôle important dans la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC, tandis qu’une augmentation de la glutamine au niveau cérébral n'est pas un facteur clé. La compréhension de ces mécanismes a entraîné la proposition de 3 nouvelles stratégies thérapeutiques potentielles pour l'EHM. Elles ciblent la diminution de l'ammoniaque sérique, la réduction du stress oxydatif et l'inhibition de la synthèse du lactate.

Ablation of primary afferent neurons by neonatal capsaicin treatment reduces the susceptibility of the portal hypertensive gastric mucosa to ethanol-induced injury in cirrhotic rats

Primary sensory afferent neurons modulate the hyperdynamic circulation in Cirrhotic rats with portal hypertension.The stomach of cirrhotic rats is prone to damage induced by ethanol, a phenomenon associated with reduced gastric hyperemic response to acid-back diffusion. The aim of this study was to examine the impact of ablation of capsaicin-sensitive neurons and the tachykinin NK(1) receptor antagonist A5330 on the susceptibility of the portal hypertensive gastric mucosa, to ethanol-induced injury and its effects on gastric cyclooxygenase (COX) and nitric oxide synthase (NOS) mRNA expression. Capsaicin was administered to neonatal, male, Wistar rats and the animals were allowed to grow. Cirrhosis was then induced by bile duct ligation in adult rats while controls had sham operation. Ethanol-induced gastric damage was assessed using ex vivo gastric chamber experiments. Gastric blood flow was measured as well as COX/NOS mRNA expression. Topical application of ethanol produced significant gastric damage in cirrhotic rats compared to controls, which was reversed in capsaicin- and A5330-treated animals. Mean arterial and portal pressure was normalized in capsaicin-treated cirrhotic rats. Capsaicin and A5330 administration restored gastric blood flow responses to topical application of ethanol followed by acid in cirrhotic rats. Differential COX and NOS mRNA expression was noted in bile duct ligated rats relative to controls. Capsaicin treatment significantly modified gastric eNOS/iNOS/COX-2 mRNA expression in cirrhotic rats. Capsaicin-sensitive neurons modulate the susceptibility of the portal hypertensive gastric mucosa to injury induced by ethanol via tachykinin NK(1) receptors and signalling of prostaglandin and NO production/release. (c) 2008 Elsevier B.V. All rights reserved.

Effects of low fat and babassu fat diets on nutritional status in obstructive cholestasis in young rats

OBJETIVO: Testar os efeitos de uma dieta com baixo teor de gordura comparada a uma dieta com gordura de babaçu sobre o estado nutricional em ratos jovens com colestase obstrutiva. MÉTODOS: Submetemos 40 ratos divididos em quatro grupos de 10 animais a partir do P21 (21º dia pós-natal) até o P49 a dois dos seguintes tratamentos: ligadura e ressecção do ducto biliar comum ou operação simulada e dieta com baixo teor de gordura (óleo de milho fornecendo 4,5% da quantidade total de calorias) ou dieta com gordura de babaçu (essa gordura fornecendo 32,7% e óleo de milho fornecendo 1,7% da quantidade total de calorias). Foi mensurado o ganho de peso a cada 4 dias do P25 ao P49. A função de crescimento de Verhulst foi ajustada aos valores de ganho de peso. A velocidade e a aceleração de crescimento nos mesmos momentos foram estimadas usando a mesma equação. Foram mensurados: quantidade de ração ingerida e ingestão energética total do P21 ao P49, utilização de energia do P25 ao P49, gordura absorvida e balanço de nitrogênio (BN) do P42 ao P49. A ANOVA com dois fatores e o método de S.N.K para comparações pareadas foram utilizados para estudar os efeitos, sobre as variáveis, da colestase e das dietas e sua interação (p<0,05). RESULTADOS: em ratos com colestase e dieta com baixo teor de gordura, houve maior velocidade de crescimento no P45, maior aceleração de crescimento no P41 e P45, maior utilização de energia, maior percentual de gordura absorvida e maior BN do que em ratos com colestase e dieta com gordura de babaçu. CONCLUSÃO: A dieta com baixo teor de gordura atenua a restrição de crescimento provocada pela colestase e proporciona melhor aproveitamento da dieta e maior incorporação da proteína ingerida do que a dieta com gordura de babaçu.

Effects of the administration of pentoxifylline and prednisolone on the evolution of portal fibrogenesis secondary to biliary obstruction in growing animals: immunohistochemical analysis of the expression of TGF-BETA; and VEGF

OBJECTIVE: During the neonatal and infancy periods, some chronic liver diseases may lead to progressive hepatic fibrosis, which is a condition that can ultimately result in the loss of organ function and severe portal hypertension necessitating hepatic transplantation. In a previous report, pharmacological interventions were demonstrated to modulate hepatic fibrosis induced by bile duct ligation in young rats. The administration of pentoxifylline or prednisolone, or the combination of both, resulted in reduced fibrogenesis in portal spaces. The objectives of the present study were to evaluate the expression of transforming growth factor beta and vascular endothelial growth factor after bile duct ligation in young rats and to assess the effect of those same drugs on cytokine expression. METHODS: In this experimental study, 80 young rats (21 or 22 days old) were submitted either to laparotomy and common bile duct ligation or to sham surgery. The animals were allocated into four groups according to surgical procedure, and the following treatments were administered: (1) common bile duct ligation + distilled water, (2) sham surgery + distilled water, (3) common bile duct ligation + pentoxifylline, or (4) common bile duct ligation + prednisolone. After 30 days, a hepatic fragment was collected from each animal for immunohistochemical analysis using monoclonal antibodies against transforming growth factor beta and vascular endothelial growth factor. Digital morphometric and statistical analyses were performed. RESULTS: The administration of pentoxifylline reduced the transforming growth factor beta-marked area and the amount of transforming growth factor beta expressed in liver tissue. This effect was not observed after the administration of prednisolone. There was a significant reduction in vascular endothelial growth factor expression after the administration of either drug compared with the non-treatment group. CONCLUSIONS: The administration of pentoxifylline to cholestatic young rats resulted in the diminished expression of transforming growth factor beta and vascular endothelial growth factor in liver tissue. The administration of steroids resulted in the diminished expression of vascular endothelial growth factor only. These pathways may be involved in hepatic fibrogenesis in young rats submitted to bile duct ligation and exposed to pentoxifylline or prednisolone.