Effects of a low-fat diet with antioxidant supplementation on biochemical markers of multiple sclerosis long-term care residents.

INTRODUCTION: Multiple sclerosis (MS) treatment options are primarily limited to immunomodulatory therapies in MS non-progressive forms. Nutrition intervention studies suggest that diet may be considered as a complementary treatment to control disease progression. Therefore, dietary intervention may help to improve wellness and ameliorate symptoms of MS patients. OBJECTIVES: To assess the effect of a low-fat diet with antioxidant supplementation on biochemical markers of institutionalized patients with progressive forms of multiple sclerosis. METHODS: A randomized prospective placebo-controlled study involving 9 participants, 5 of them assigned to the intervention group (low-fat diet and antioxidant supplementation) and the other 4 to the placebo group (low-fat diet). The effect of the dietary intervention, involving diet modification and antioxidant supplementation, was examined for 42 days by measuring anthropometric, biochemical parameters and oxidative stress markers in blood at baseline (day 0), intermediate (day 15) and end (day 42) stages of the treatment. RESULTS: The intervention group obtained C reactive protein levels significantly lower than those observed in the corresponding placebo group at the end of the study. Oxidative stress and inflammatory markers isoprostane 8-iso-PGF2α and interleukine IL-6 values also diminished after dietary intervention in the intervention group. Catalase activity increased significantly in the intervention group prior antioxidant supplementation. No significant differences were observed in other oxidative stress markers. CONCLUSIONS: The results suggest that diet and dietary supplements are involved in cell metabolism modulation and MS-related inflammatory processes. Consequently, low fat diets and antioxidant supplements may be used as complementary therapies for treatment of multiple sclerosis.

Introducción: Las posibilidades de tratamiento de la esclerosis múltiple (EM) se encuentran limitadas principalmente a terapias con inmumoduladores en las formas no progresivas de EM. Los estudios de intervención nutricional sugieren que la dieta puede considerarse como un tratamiento alternativo para controlar la progresión de la enfermedad. Por esta razón, las intervenciones en la dieta pueden ayudar a mejorar el bienestar y mejorar los síntomas de los pacientes con EM. Objetivos: Valorar el efecto de una dieta pobre en grasas con suplementación de antioxidantes en los marcadores bioquímicos de pacientes institucionalizados que presentan formas progresivas de EM. Métodos: Se realizó un estudio prospectivo aleatorizado controlado por placebo con 9 participantes, 5 de los cuales se asignan al grupo de intervención (dieta baja en grasas y suplementación antioxidante) y los 4 restantes al grupo placebo (dieta baja en grasas). Se evaluó el efecto de la intervención dietética que supone modificación de la dieta e introducción de antioxidantes durante 42 días mediante valoraciones de parámetros antropométricos y bioquímicos y marcadores del estrés oxidativo en sangre y orina en las etapas inicial (día 0), intermedia (día 15) y final (día 42) del tratamiento. Resultados: Se obtuvieron niveles de proteína C reactiva significativamente inferiores en el grupo de intervención con respecto al grupo placebo al final del estudio. Los marcadores de estrés oxidativo e inflamación: isoprostanos 8-iso-PGF2e interleucina IL-6 también disminuyeron en el grupo de intervención después de la intervención dietética. La actividad de la enzima catalasa aumentó de forma significativa en el grupo de intervención antes de la suplementación con antioxidantes. No se observaron diferencias significativas en otros marcadores de estrés oxidativo. Conclusiones: Los resultados obtenidos sugieren que la dieta y los suplementos dietéticos están involucrados en la modulación del metabolismo celular y los procesos de inflamación de la EM. En consecuencia, las dietas bajas en grasas y los suplementos antioxidantes podrían ser utilizados como terapias alternativas en el tratamiento de la EM.

Non-alcoholic steatohepatitis: what can we learn from animal models?

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of abnormal liver function and correlates with central adiposity, obesity, insulin resistance, the metabolic syndrome and type 2 diabetes mellitus. The pathological spectrum of NAFLD ranges from fatty liver to non-alcoholic steatohepatitis (NASH), advanced fibrosis, cirrhosis, and even hepatocellular carcinoma. Though NAFLD and NASH are becoming a major public health problem, ethical constraints on obtaining human liver tissue limit the interpretability of the data and the ability to delineate cause and effect from complex, interactive disease pathogenic pathways. Animal models of NASH can provide critical information leading to identify potential drug targets and to understand their molecular mechanisms, and are platforms for compound screening in drug development and for the assessment of novel therapeutic strategies. This review is aimed to offer an updated overview of the nutritional, genetic and pharmacologic animal models of NASH. Though the information derived from these models has clear relevance for the comprehension of the molecular basis of human disease, most of them fail to reproduce the full spectrum of liver pathology and the metabolic context that characterizes human NASH. Consequently, it is necessary to establish animal models that can best mimic the actual etiology, progression, and pathogenesis of the disease, and prove effectiveness for examining and selecting compounds with potential therapeutic benefit in NASH.

Potential of flavonoids as anti-inflammatory agents: modulation of pro-inflammatory gene expression and signal transduction pathways.

Flavonoids are a large class of naturally occurring compounds widely present in fruits, vegetables, and beverages derived from plants. Reports have suggested that these compounds might be useful for the prevention of a number of diseases, partly due to their anti-inflammatory properties. It has been demonstrated that flavonoids are able to inhibit expression of isoforms of inducible nitric oxide synthase, ciclooxygenase and lipooxygenase, which are responsible for the production of a great amount of nitric oxide, prostanoids and leukotrienes, as well as other mediators of the inflammatory process such as cytokines, chemokines or adhesion molecules. Modulation of the cascade of molecular events leading to the over-expression of those mediators include inhibition of transcription factors such as nuclear factor kappa B, activator protein 1, signal transducers and activators of transcription, CCAAT/enhancer binding protein and others. Effects on the binding capacity of transcription factors may be regulated through the inhibition of protein kinases involved in signal transduction, such as mitogen activated protein kinases. Although the numerous studies published with in vitro approaches allow identifying molecular mechanisms of flavonoid effects, the limited bioavailability of these molecules makes necessary validation in humans. Whatever the case, the data available make clear the potential utility of dietary flavonoids or new flavonoid-based agents for the possible treatment of inflammatory diseases. The present review summarizes recent research data focusing on the modulation of the expression of different inflammatory mediators by flavonoids and the effects on cell signaling pathways responsible for their anti-inflammatory activity.

Apoptotic signaling pathways as a target for the treatment of liver diseases.

Dysregulation of apoptosis is a major contributor to the initiation and aggravation of liver injury. Agents that modulate apoptosis may be of therapeutic benefit in a number of liver diseases, and research related to cell type-specific activation or inhibition of apoptotic signaling pathways will provide new strategies for treatment.

Anti-inflammatory properties of dietary flavonoids.

Flavonoids are a group of natural substances that are located in sources of vegetal origin. More than 4,000 varieties of flavonoids have been identified. All of them are phenyl-benzopyrones of low molecular weight with a basic structure formed by two benzene rings united through a heterocyclic pyrane or pyrone. Besides their relevance in plants, flavonoids are important for human health. Their antioxidant capacity confers a therapeutic potential in cardiovascular diseases, gastric or duodenal ulcers, cancer or hepatic pathologies. Also important are their antiviral and anti-allergic actions, as well as their anti-thrombotic and anti-inflammatory properties. Prostaglandins and nitric oxide biosynthesis is involved in inflammation, and isoforms of inducible nitric oxide synthase (iNOS) and of cyclooxygenase (COX-2) are responsible for the production of a great amount of these mediators. It has been demonstrated that flavonoids are able to inhibit both enzymes, as well as other mediators of the inflammatory process such as reactive C protein or adhesion molecules. Modulation of the cascade of molecular events leading to the overexpression of those mediators include inhibition of transcription factors such as nuclear factor kappa B and AP-1, through the inhibition of protein kinases involved in signal transduction. Increased antioxidant defenses through activation of the NF-E2 related factor 2 (Nrf2) also contribute to the anti-inflammatory capacity of flavonoids.

[Animal models of fulminant hepatic failure]. / Modelos animales de fallo hepático fulminante.

Fulminant hepatic failure (FHF) is a very serious clinical sindrome that, in spite of the important therapeutical advances that have taken place in the last years by means of bioartifical hepatic support devices and hepatic transplantation, is still associated to a high mortality. Knowledge and treatment of the FHF have been limited by the lack of satisfactory animal models. Among the attempts to develop a suitable model are surgical models, such as hepatectomy and total and/or partial devascularization, or the use of chemical substances with hepatic toxicity, such as acetaminophen, azoximethane, galactosamine or thioacetamide, among others. However, most of these models do not adequatly reflect the pattern of the human disease and all of them present important limitations. Although viral hepatitis is one of the most frequent causes of FHF, the use of viral agents to develop animal models has been little and unfortunate. Our group has recently developed a viral animal model of FHF by means of the inoculation of rabbits with the virus of the rabbit hemorrhagic disease. This model displays biochemical, and histological characteristics, and clinical signs that ressemble those in human FHF. In the present article, the most widely used animal models of FHF, together with their main advantages and disadvantages, are presented.

N-acetyl-cysteine protects liver from apoptotic death in an animal model of fulminant hepatic failure.

BACKGROUND: This work was undertaken to investigate whether treatment with N-acetyl-cysteine (NAC) prevents oxidative stress and inhibits the apoptotic pathways in an animal model of fulminant hepatic failure. METHODS: Rabbits were experimentally infected with 2x10(4) hemagglutination units of a rabbit hemorrhagic disease virus isolate. RESULTS: The spontaneous mortality rate of infected animals was 67% at 36 h post infection (pi) and 90% at 48 h pi. This percentage decreased significantly in animals receiving an i.p. injection of NAC (150 mg/kg body way/daily), for 7 days prior to infection. From 36 h pi marked increases were detected in blood levels of transaminases, lactate dehydrogenase, bilirubin and the oxidised/reduced glutathione ratio. All these effects were significantly prevented by NAC treatment. The Bax to Bcl-2 relative expression, the expression of FasL, cytochrome c and PARP-1, and the activity of caspase 3 were significantly increased at 36 and 48 h pi in infected animals. These changes were markedly reduced in animals treated with NAC, with the exception of FasL. CONCLUSION: Our results suggest a potential hepatoprotective role of NAC in fulminant hepatic failure, mediated partially through the modulation of the intrinsic pathway of apoptosis.

[Effects of glutamine on antioxidants systems and hepatic detoxification in rats: influence of formulation]. / Influencia de la formulación de la glutamina en sus efectos sobre los sistemas antioxidantes y de destoxificación hepática en la rata.

GOALS: The goal of this study is to assess the effect that supplementing parenteral diets with L-glutamine or with L-alanyl-L-glutamine has on the balance of oxidants/antioxidants in the liver and on detoxification systems mediated by P-450 cytochrome in rats. MATERIAL AND METHODS: Central catheters were inserted in the animals (n = 60) and they were randomly assigned to one of the following groups: a control group (C) with oral feeding and I.V. infusion of saline solution, a total parenteral nutrition group without glutamine (TPN without GLN), a parenteral nutrition group with glutamine supplement (TPN GLN), and a total parenteral nutrition group with a supplement of alanine-glutamine dipeptide (20 g/L) (TPN ALA-GLN). The parenteral nutrition provided was all isocaloric and isonitrogenated, and the infusions were administered at a speed of 2 ml/h over 5 days. RESULTS: In the animals of the group without GLN, the liver concentration of glutathione was reduced while the levels of thiobarbituric acid reaction products (TBARS) increased. Supplementing with either glutamine or alanine-glutamine normalized the levels of glutathione but the TBARS levels only fell in the group with the dipeptide. This effect was parallel to the partial recovery of the antioxidant enzyme activities analyzed. The liver concentrations of P-450 cytochrome, P-450 cytochrome dependent mono-oxygenases and the clearance of antipyrine were not modified by the supplements of glutamine or alanine-glutamine. CONCLUSIONS: Our data suggest a greater protection by alanine-glutamine supplements against the injury produced by free radicals during TPN and the absence of any effect with either glutamine or alanine-glutamine supplements on the oxidative metabolism of the liver.

Effects of aging and cyclosporin treatment on the hepatobiliary efflux of glutathione.

The aim of this study was to investigate the effects of cyclosporin (CyA) treatment on biliary glutathione efflux in rats of different ages (1, 2, 4, and 24 months). CyA treatment reduced the liver content of total glutathione in 1-, 2- and 24 month old rats (-30%, -43% and -30%, respectively). By contrast, oxidized glutathione (GSSG) concentration in liver tended to increase, although non significantly, in the rats aged 4 and 24 month (+36% and +28%, respectively). The oxidized-to-reduced glutathione ratio was significantly increased in 2-, 4- and 24 month old animals (+23%, +36% and >100%, respectively). Regarding biliary glutathione, our data indicate that efflux rates of total glutathione in control (untreated) rats increased to a maximum at 4 months, and decreased (-56%) in 24 month old rats, although values were still higher than those from young animals. CyA treatment significantly reduced biliary glutathione secretion except in 24 month old rats (-98%, -66% and -32%, at 1, 2 and 4 month, respectively). In addition, following inhibition of the intrabiliary catabolism of the tripeptide by acivicin, glutathione efflux rates into bile were significantly reduced by the drug only in 1- and 2 month old rats (-29% and -55%, respectively) and even tended to increase, although non significantly, in oldest animals. Our data indicate that inhibition of biliary glutathione efflux by CyA was greater in younger rats and support the view that increased intrabiliary catabolism of the tripeptide and inhibition of its canalicular transport could contribute to the decline in biliary glutathione secretion induced by the drug.

Diagnostic imaging in sheep hepatic fascioliasis: ultrasound, computer tomography and magnetic resonance findings.

Radiological features and biochemical changes were investigated during the parenchymal and ductal phases of chronic Fasciola hepatica infection in sheep. The activities of plasma aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT), plasma levels of IgG anti- F. hepatica and serial ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) findings were studied in eight sheep infected with 150 F. hepatica metacercariae. Experimental fluke infection provoked an increase in plasma level of IgG directed against F. hepatica and in plasma LDH and AST activities from 4 weeks after infection. Enzyme activities did not significantly differ from the baseline after 15 and 12 weeks for LDH and AST, respectively. GGT activity increased from 9 weeks postinfection and still remained significantly elevated at 18 weeks. In the parenchymal phase, both CT and MRI showed nodular lesions in five animals and MRI could also detect early tracks in the subcapsular area in three sheep. Ultrasound findings were nonspecific in this phase. Ductal dilatation was shown by ultrasound, CT and MRI in almost all animals, although MRI was inferior to CT in depicting a mild ductal dilatation. Moving echogenic forms in the dilated bile ducts were observed by ultrasound from 9 weeks postinfection in seven of the eight sheep. Moving worms were only demonstrated in four sheep at CT and in a single sheep at MRI. This study shows that radiological findings may be useful in studies of fluke-induced liver damage.

[Flavonoids: properties and anti-oxidizing action]. / Los flavonoides: propiedades y acciones antioxidantes.

Flavonoids are phenolic compounds that represent substantial constituents of the non-energetic part of the human diet. They are naturally found in vegetables, berries, fruits, wine and beer. There are more than 5000 different flavonoids. The average intake depend on the country but the average intake is approximately 23 mg/day; quercetin is predominant at 16 mg/day. Flavonoids were considered initially to be substances without any benefit for humans. Later, it has been reported that they exert multiple biological effects due to their antioxidant and free radical-scavenging abilities. Although results from different studies have demonstrated that flavonoids can act as pro-oxidant at very high doses, most investigations have reported anti-inflammatory, antiviral, or anti-allergic effects and a protective role in heart diseases, cancer and different pathologies.

Effects of aging on the susceptibility to the toxic effects of cyclosporin A in rats. Changes in liver glutathione and antioxidant enzymes.

Free radicals are involved in aging and cyclosporin A-induced toxicity. The age-related changes in the liver oxidative status of glutathione, lipid peroxidation, and the activity of the enzymatic antioxidant defense system, as well as the influence of aging on the susceptibility to the hepatotoxic effects of cyclosporin (CyA) were investigated in rats of different ages (1, 2, 4, and 24 months). The hepatic content of reduced glutathione (GSH) increased with aging, peaked at 4 months, and decreased in senescent rats. By contrast, glutathione disulfide (GSSG) and thiobarbituric acid-reactive substances (TBARS) concentrations and superoxide dismutase, catalase, and glutathione peroxidase activities were higher in the oldest than in the youngest rats. CyA treatment, besides inducing the well-known cholestatic syndrome, increased liver GSSG and TBARS contents and the GSSG/GSH molar ratio, and altered the nonenzymatic and enzymatic antioxidant defense systems. The CyA-induced cholestasis and hepatic depletion of GSH, and the increases in the GSSG/GSH ratio, and in GSSG and TBARS concentrations were higher in the older than the mature rats. Moreover, superoxide dismutase and catalase activities were found to be significantly decreased only in treated senescent rats. The higher CyA-induced oxidative stress, lipoperoxidation, and decreases in the antioxidant defense systems in the aged animals render them more susceptible to the hepatotoxic effects of cyclosporin.

The flavonoid quercetin ameliorates liver damage in rats with biliary obstruction.

BACKGROUND/AIMS: Our aim was to investigate whether the antioxidant quercetin might protect against liver injury in chronically biliary obstructed rats. METHODS: Secondary biliary cirrhosis was induced by 28 days of bile duct obstruction. Animals received quercetin at 75, 150 and 300 micromol x kg body wt(-1) x day(-1) i.p. through the experimental period or at 150 micromol x kg body wt(-1) x day(-1) i.p. for the last 2 weeks. RESULTS: Bile duct obstruction resulted in a decrease in the activities of antioxidant enzymes. Liver oxidised/reduced (GSSG/GSH) glutathione ratio, hepatic and mitochondrial thiobarbituric acid reactive substances (TBARS) and collagen content were significantly increased and a marked fibrosis and bile ductular proliferation was observed. Quercetin corrected the reduction in glutathione concentration and partially prevented the increase in collagen concentration, TBARS and GSSG/GSH ratio. Treatment resulted in a significant preservation of the activities of antioxidant enzymes, a less pronounced fibrosis and a marked inhibition of bile ductular proliferation. Maximal effects were reached with the intermediate quercetin dose given for 2 or 4 weeks. CONCLUSIONS: Quercetin reduces liver oxidative damage, ductular proliferation and fibrosis in biliary-obstructed rats. These effects suggest that it might be a useful agent to preserve liver function in patients with biliary obstruction.

Morphologic and biochemical changes caused by experimentally induced dicroceliosis in hamsters (Mesocricetus auratus).

BACKGROUND AND PURPOSE: The aim of the study reported here was to investigate the pathomorphologic changes caused by experimentally induced dicroceliosis and their correlation with hepatobiliary function. METHODS: Studies were carried out at days 80 and 120 after oral inoculation of hamsters with 40 metacercariae of Dicrocoelium dendriticum. RESULTS: The parasite-induced pathologic changes were assessed by presence of fluke eggs in feces, increased plasma alanine transaminase and aspartate transaminase activities and morphologic alterations. Dicroceliosis was characterized by bile ductular proliferation and enlargement of the bile duct surface area caused by hyperplastic cholangitis in septal bile ducts. The liver from infected animals contained portal tracts infiltrated with small to moderate numbers of lymphocytes, macrophages, and eosinophils. Simultaneously, there was an increase in portal tract collagen that extended to the interlobular septa and caused pressure atrophy of the hepatic parenchyma. The concentration of thiobarbituric acid-reactive substances and the ratio of oxidized to reduced glutathione, measured as markers of oxidative stress, were significantly increased. CONCLUSIONS: The presence of oxidative alterations could be related to the morphologic evidence of chronic inflammatory response as well as to liver cellular injury indicated by cellular swelling, and increased presence of peroxisomes and lysosomes.

Effects of parenteral nutrition supplemented with glutamine or glutamine dipeptides on liver antioxidant and detoxication systems in rats.

Our aim was to determine the effects of glutamine or alanyl glutamine parenteral supplementation on the liver oxidant/antioxidant balance and on cytochrome-P450-mediated detoxication in rats. Animals were infused for 5 d with standard total parenteral nutrition (TPN), glutamine-enriched TPN, or alanyl glutamine-enriched TPN. The hepatic concentration of glutathione was reduced, and the levels of thiobarbituric-acid-reactive substances (TBARS) were increased in animals receiving standard TPN. Both glutamine and alanyl glutamine supplementation normalized glutathione, but thiobarbituric-acid-reactive substance concentration was only decreased by ananyl glutamine. This effect was parallel to a partial recovery of the activity of antioxidant enzymes. Cytochrome-P450 liver content, cytochrome-P450-dependent monooxygenases, and antipyrine clearance were not modified by glutamine or alanyl glutamine. Our data suggest a better protection against free radicals by alanyl glutamine supplementation and an absence of effects of both glutamine and alanyl glutamine on liver oxidative metabolism.

Liver blood flow changes during laparoscopic surgery in pigs. A study of hepatic indocyanine green removal.

BACKGROUND: Physiological effects caused by abdominal insufflation in the course of laparoscopic surgery are partially unknown. The purpose of the present study was to determine if indocyanine green (ICG) pharmacokinetic parameters, as an index of hepatic blood flow, change during laparoscopic surgery in the presence of a CO2 pneumoperitoneum. This effect could cause important alterations in the kinetics of anesthetic drugs. METHODS: Eighteen female pigs were anaesthetized under constant ventilation and randomly assigned to three groups undergoing insufflation with CO2 (I), laparoscopic oophorectomy with CO2 pneumoperitoneum (LS), or oophorectomy by open surgery (OS). CO2 pneumoperitoneum was performed at 14 mmHg. ICG (1 mg/kg) was injected into a marginal vein on two separate occasions: 30 min before and 30 min after the start of insufflation or surgery. Blood was sampled from the carotid artery at time intervals after the injection of ICG and after pharmacokinetic parameters were obtained by a computer program. RESULTS: The area under the curve (AUC0-infinity) indicated important dysfunctions in ICG availability in all three groups of animals, with significant increases of 104%, 82%, and 48% for groups I, LS, and OS, respectively. The ICG apparent half-life did not significantly change in group OS, but it rose in groups I (+17%) and LS (+28%). ICG clearance was significantly reduced by 32% in group OS and to a larger extent in groups I and LS (-45% and -46%, respectively). CONCLUSION: These findings confirm the contribution of CO2 pneumoperitoneum to decreased liver blood flow during laparoscopic surgery.

Oxidative stress and changes in liver antioxidant enzymes induced by experimental dicroceliosis in hamsters.

The purpose of our study was to assess the effects of experimental dicroceliosis on the antioxidant defense capability of the liver in hamsters. Studies were carried out at 80 and 120 days after infection with an oral dose of 40 metacercariae of Dicrocoelium dendriticum. The parasitic pathology was ascertained by the presence of fluke eggs in feces, increased serum ALT and AST activities, and histological findings. The concentration of thiobarbituric acid-reactive substances (TBARS) and the ratio of oxidized to reduced glutathione (GSSG/GSH), measured as markers of oxidative stress, were significantly increased [TBARS: +40% and +84% at 80 and 120 days postinfection (p.i.), respectively; GSSG/GSH: +200% and +117%]. Dicroceliosis increased Se-dependent glutathione peroxidase (GPx) activity in both cytosol (+24% and +46%) and mitochondria (+73% and +41%). Superoxide dismutase activity was significantly reduced in cytosol (-19% and -38%) and mitochondria (-20% and -39%). No significant change was found in the activity of Se-independent GPx or catalase. The ratio of glutathione peroxidase/glutathione reductase at 80 and 120 days p.i. was increased by 25% and 63%, respectively. Gamma-glutamyl cysteinyl synthetase activity was increased by 27% and 20%, respectively. Our data indicate that although dicroceliosis courses with activation of antioxidant enzymes and glutathione synthesis, inefficient scavenging of reactive oxygen species takes place, resulting in oxidative liver damage.

Enhanced bile formation induced by experimental dicrocoeliosis in the hamster.

The purpose of this investigation was to determine the effects of experimental dicrocoeliosis on bile formation in the hamster. Studies were carried out at 120 days after infection with an oral dose of 40 metacercariae of Dicrocoelium dendriticum. A significant elevation in bile flow (+20%) and in the biliary output of glutathione (+34%), bile acid (+59%), cholesterol (+108%), phospholipids (+99%) and alkaline phosphatase (+36%) was observed in the infected animals. The bile-to-plasma [14C] mannitol ratio increased to values greater than 1 and there was a reduced contribution (-26%) of biliary tree to bile formation. Those data suggest that enhancement in choleresis had a canalicular origin. The presence of oxidative stress, evidenced by the increased oxidized/reduced glutathione ratio and TBARS concentrations, may contribute to the elevated glutathione efflux into bile. Enhancement in bile acid output was not due to qualitative or quantitative changes in bile acid metabolism, as indicated by the absence of significant modification in liver cholesterol 7alpha-hydroxylase activity and bile acid profile in bile. Increase in the ability of the canalicular membrane to export bile acids was not involved, since maximal secretion rate for exogenously administered taurocholate was decreased. When bile flow, bile acid and biliary lipid secretion was determined in colchicine-pretreated animals differences between control and infected animals were abolished, suggesting that stimulation of the transcytotic vesicle pathway plays an important role in the alteration of the biliary function caused by dicrocoeliosis.

Cholestasis and alterations of glutathione metabolism induced by tacrolimus (FK506) in the rat.

BACKGROUND: Tacrolimus (FK506) is an immunosuppressive agent used for the prevention of allograft rejection after organ transplantation. The aim of this study was to investigate the effects of chronic tacrolimus treatment on bile secretion in rats. METHODS: Tacrolimus was administered intraperitoneally at doses of 0.2, 0.5, and 0.8 mg/kg/day for 6 weeks. RESULTS: Bile flow was significantly reduced at doses of 0.5 mg/kg and 0.8 mg/kg (-25% and -32%, respectively). Bile acid secretion was not significantly modified, but bicarbonate secretion decreased at doses of 0.5 mg/kg and 0.8 mg/kg (-23% and -29%, respectively). Glutathione secretion was significantly reduced at doses of 0.5 mg/kg (-29%) and 0.8 mg/kg (-49%). Liver glutathione concentration was reduced at the higher dose (-17%). Liver gamma-glutamyl-cysteinyl synthetase activity was elevated (+22%, +10, and +15%) and gamma-glutamyl transpeptidase activity was reduced (-18%, -40%, and -25%) at all doses. Dichlorofluorescein and thiobarbituric acid-reactive substance concentrations were not significantly modified. Liver glutathione peroxidase activity increased at doses of 0.5 mg/kg (+65%) and 0.8 mg/kg (+56%). Kidney concentration of thiobarbituric acid-reactive substances was significantly increased at doses of 0.5 mg/kg (+17%) and 0.8 mg/kg (+12%). CONCLUSIONS: Our data indicate that tacrolimus at high doses induces cholestasis by inhibiting primarily biliary excretion of glutathione and, to a lesser extent, bicarbonate. The decrease in biliary glutathione secretion is not due to a lower synthesis or degradation and could be related to its increased sinusoidal efflux.

Effects of experimental dicrocoeliosis on oxidative drug metabolism in hamster liver.

The purpose of this investigation was to determine the effects of experimental dicrocoeliosis on the hepatic oxidative drug-metabolizing system in hamsters. Studies were carried out 80 and 120 days after infestation with an oral dose of 40 metacercariae of Dicrocoelium dendriticum. The parasitic pathology was ascertained by detection of the fluke eggs in faeces, increased serum alanine aminotransferase and aspartate aminotransferase activities, and postmortem and histological findings. Cytochrome P-450 concentration, aniline hydroxylase activity and ethoxycoumarin O-deethylase activity were significantly decreased in both groups of infected animals. Aminopyrine N-demethylase activity and erythromycin N-demethylase activity were only reduced 120 days after infection. Effects on drug metabolizing enzymes were unrelated to changes in the physical state of the microsomal membrane, as assessed by measurement of fluorescence polarization. The results of this study indicate that the capacity of the liver for handling drugs and xenobiotics may be impaired as a consequence of dicrocoeliosis.