Microsomal function in biliary obstructed rats: effects of S-adenosylmethionine

Treatment with S-adenosylmethionine ameliorates irinotecan-induced intestinal barrier dysfunction and intestinal microbial disorder in mice

This study aimed to investigate the protective effects of S-adenosylmethionine (SAM) on irinotecan-induced intestinal barrier dysfunction and microbial ecological dysregulation in both mice and human colon cell line Caco-2, which is widely used for studying intestinal epithelial barrier function. Specifically, this study utilized Caco-2 monolayers incubated with 7-ethyl-10-hydroxycamptothecin (SN-38) as well as an irinotecan-induced diarrhea model in mice. Our study found that SAM pretreatment significantly reduced body weight loss and diarrhea induced by irinotecan in mice. Furthermore, SAM inhibited the increase of intestinal permeability in irinotecan-treated mice and ameliorated the decrease of Zonula occludens-1(ZO-1), Occludin, and Claudin-1 expression. Additionally, irinotecan treatment increased the relative abundance of Proteobacteria compared to the control group, an effect that was reversed by SAM administration. In Caco-2 monolayers, SAM reduced the expression of reactive oxygen species (ROS) and ameliorated the decrease in transepithelial electrical resistance (TER) and increase in fluorescein isothiocyanate-dextran 4000 Da (FD-4) flux caused by SN-38. Moreover, SAM attenuated changes in the localization and distribution of ZO-1and Occludin in Caco-2 monolayers induced by SN-38 and protected barrier function by inhibiting activation of the p38 MAPK/p65 NF-κB/MLCK/MLC signaling pathway. These findings provide preliminary evidence for the potential use of SAM in treating diarrhea caused by irinotecan.

Betaine suppresses cell proliferation by increasing oxidative stress-mediated apoptosis and inflammation in DU-145 human prostate cancer cell line

Prostate cancer is the main cause of cancer-related mortality in men around the world and an important health problem. DU-145 human prostate cancer cells provide an opportunity to investigate prostate cancer. Betaine has a number of anticancer effects, such as inactivation of carcinogens, inhibition of cancer cell proliferation, angiogenesis, and metastasis. However, there is no study investigating the effects of betaine on DU-145 cells. The aim of this study was to evaluate the effects of different concentrations of betaine on the oxidative stress, apoptosis, and inflammation on DU-145 cells. Firstly, we proved the cytotoxic activity of betaine (0 to 150 mg/ml) on DU-145 cells by using 3-(4, 5-dimethylthiazol, 2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) and defined the optimal concentration of betaine. Then, by employing the doses found in MTT, the levels of antioxidant (GSH, SOD, CAT, and TAS) and oxidant (MDA and TOS) molecules, pro-inflammatory cytokines (TNF-a and IL-6), apoptotic proteins (CYCS and CASP3), and DNA fragmentation were measured. Morphological changes and apoptosis were evaluated using H&E technique, Bax and Bcl-2 immunohistochemistry. Results suggested that betaine caused oxidative stress, inflammation, inhibition of cell growth, apoptosis, and morphological alterations in DU-145 cells dose-dependently. Furthermore, treatments with increasing betaine concentrations decreased the antioxidant levels in cells. We actually revealed that betaine, known as an antioxidant, may prevent cell proliferation by acting as an oxidant in certain doses. In conclusion, betaine may act as a biological response modifier in prostate cancer treatment in a dose-dependent manner.

Lower methionine/cystine ratio in low-protein diet improves animal reproductive performance by modulating methionine cycle

BACKGROUND

As the extend of low-protein diets in many countries including China, more researches of amino acid nutrition (AA) have been carried out. But the ideal AA pattern, especially the reasonable proportion of amino acids such as the desired methionine (Met): cystine (Cys) ratios are not yet clear.

OBJECTIVES

In this article, the experiments of low-protein diet with varying ratios of Met:Cys (low ratio of 1:3, medium ratio of 1:1, and high ratio of 3:1) were conducted to investigate the effect on mice growth and reproductive performance.

RESULTS

The result indicated that the lower Met:Cys ratio improves reproductive performance in male mice, but the growth performance were no change in all groups. Meanwhile, the abnormality rate of sperm increased as the ratio of methionine and cystine increased. Quantitative analysis showed that the low Met:Cys ratio has obviously decreased the expression of Bax protein and the concentrations of testosterone in male serum, but Prm2, Pgk2, Bcl-2, Bak1, and AR gene were made no difference. Furthermore, different Met:Cys ratios have significant effects on the modulated methionine cycle by increasing the expressions of MAT2B, GNMT, and BHMT in low Met:Cys ratio. On the other hand, it was also found that there were increases in GSH-Px enzyme activities and decreases in MDA levels in male serum.

CONCLUSIONS

Overall, the present study showed that a dietary lower Met:Cys ratio in a low-protein diet had a positive influence on the reproductive performance of male animal through obviously improving sperm quality and antioxidant capacity, and inhibiting apoptosis. And the study provided new pieces of evidence to re-evaluate the role of precise sulfur amino acid nutrition in a low-protein diet.

Betaine in Inflammation: Mechanistic Aspects and Applications

Betaine is known as trimethylglycine and is widely distributed in animals, plants, and microorganisms. Betaine is known to function physiologically as an important osmoprotectant and methyl group donor. Accumulating evidence has shown that betaine has anti-inflammatory functions in numerous diseases. Mechanistically, betaine ameliorates sulfur amino acid metabolism against oxidative stress, inhibits nuclear factor-κB activity and NLRP3 inflammasome activation, regulates energy metabolism, and mitigates endoplasmic reticulum stress and apoptosis. Consequently, betaine has beneficial actions in several human diseases, such as obesity, diabetes, cancer, and Alzheimer's disease.

Ablation of β,β-carotene-9',10'-oxygenase 2 remodels the hypothalamic metabolome leading to metabolic disorders in mice

β,β-Carotene-9',10'-oxygenase 2 (BCO2) is a protein localized to the inner membrane of mitochondria. It was initially discovered as an enzyme that catalyzes the asymmetric cleavage of carotenoids. Systemic depletion of BCO2 causes increased food intake and impaired hepatic lipid metabolism in mice. The aim of this current study was to determine the extent to which BCO2 exerts its role in hypothalamic nutrient metabolism and feeding behavior through remodeling the hypothalamic metabolome in mice. Male BCO2 knockout (KO) and the isogenic wild-type 129S6 (WT) mice at 6 weeks of age were used for metabolic and cytokine and hypothalamic metabolomics and biochemical analysis. Compared to the WT, BCO2 KO mice exhibited widespread disruptions in metabolism and metabolite homeostasis, an increase in fasting blood glucose, a decrease in circulating glucagon and leptin, an elevation of plasma interleukin 1 beta and tumor necrosis factor alpha, and impaired AMP-activated protein kinase signaling. The global hypothalamic metabolomic results revealed that depletion of BCO2 resulted in striking metabolic changes, including suppression of long-chain fatty acids transport into mitochondria, inhibition of the metabolism of dipeptides and sulfur-containing amino acids, and stimulation of local oxidative stress and inflammation in the hypothalamus of BCO2 KO mice. These findings suggest that BCO2 regulates hypothalamic mitochondrial function, nutrient metabolism, and local oxidative stress and inflammation. Complex interplay between the hormone signaling and impaired lipid and glucose metabolism could account for initiation of oxidative stress, inflammation and eventual metabolic disorders in BCO2 KO mice.

Antioxidant Mechanism of Betaine without Free Radical Scavenging Ability

Betaine (BET) is a native compound widely studied as an antioxidant in agriculture and human health. However, the antioxidant mechanism of BET remains unclear. In this research, radical scavenging assays showed that BET had little free radical scavenging activity. However, the antioxidant activity of BET was confirmed by cellular antioxidant activity (CAA) and erythrocyte hemolysis assays. The results of quantitative PCR (qPCR) and enzyme activity determination kits showed that the antioxidant activity of BET was not due to the gene expression and activity of antioxidases. High-pressure liquid chromatography (HPLC) assessment of the effect of BET on sulfur-containing amino acid metabolism showed that BET increased the levels of nonenzymatic antioxidants,S-adenosylmethionine (SAM) and methionine (p < 0.05), via the regulation of the methionine-omocysteine cycle. Additionally, the three methyl groups of BET were found to play a key role in its antioxidant activity. The possible reason was that because of the hydrophobicity of the three methyl groups and hydrophilicity of the carboxyl of BET, a tight protective membrane was formed around cells to prevent oxidative stress inducer from inducing ROS generation and cell damage. In conclusion, the antioxidant mechanism of BET was found to enhance nonenzymatic antioxidant defenses via the methionine-homocysteine cycle and form a protective membrane around cells.

Swimming training induces liver mitochondrial adaptations to oxidative stress in rats submitted to repeated exhaustive swimming bouts

BACKGROUND AND AIMS

Although acute exhaustive exercise is known to increase liver reactive oxygen species (ROS) production and aerobic training has shown to improve the antioxidant status in the liver, little is known about mitochondria adaptations to aerobic training. The main objective of this study was to investigate the effects of the aerobic training on oxidative stress markers and antioxidant defense in liver mitochondria both after training and in response to three repeated exhaustive swimming bouts.

METHODS

Wistar rats were divided into training (n = 14) and control (n = 14) groups. Training group performed a 6-week swimming training protocol. Subsets of training (n = 7) and control (n = 7) rats performed 3 repeated exhaustive swimming bouts with 72 h rest in between. Oxidative stress biomarkers, antioxidant activity, and mitochondria functionality were assessed.

RESULTS

Trained group showed increased reduced glutathione (GSH) content and reduced/oxidized (GSH/GSSG) ratio, higher superoxide dismutase (MnSOD) activity, and decreased lipid peroxidation in liver mitochondria. Aerobic training protected against exhaustive swimming ROS production herein characterized by decreased oxidative stress markers, higher antioxidant defenses, and increases in methyl-tetrazolium reduction and membrane potential. Trained group also presented higher time to exhaustion compared to control group.

CONCLUSIONS

Swimming training induced positive adaptations in liver mitochondria of rats. Increased antioxidant defense after training coped well with exercise-produced ROS and liver mitochondria were less affected by exhaustive exercise. Therefore, liver mitochondria also adapt to exercise-induced ROS and may play an important role in exercise performance.

The effects of hyperbaric oxygen application against cholestatic oxidative stress and hepatic damage after bile duct ligation in rats

BACKGROUND

The aim of this study was to evaluate the preventive and therapeutic potential of hyperbaric oxygen therapy (HBO) on the liver tissue against bile duct ligation (BDL)-induced oxidative damage and fibrosis in rats.

MATERIALS AND METHODS

We divided 32 adult male Sprague Dawley rats into four groups: sham, sham plus HBO, BDL, and BDL plus HBO; each group contained eight animals. We placed the sham plus HBO and BDL plus HBO groups in an experimental hyperbaric chamber in which we administered pure oxygen at 2.5 atmospheres absolute 100% oxygen for 90 min on 14 consecutive days.

RESULTS

The application of BDL clearly increased the tissue malondialdehyde level, myeloperoxidase activity, and hydroxyproline content and decreased the antioxidant enzymes (superoxide dismutase and catalase activities) and glutathione level. Hyperbaric oxygen therapy treatment significantly decreased the elevated tissue malondialdehyde level, myeloperoxidase activity, and hydroxyproline content and increased the reduced superoxide dismutase and catalase activities and glutathione level in the tissues. The changes demonstrating the bile duct proliferation and fibrosis in expanded portal tracts include the extension of proliferated bile ducts into lobules, mononuclear cells, and neutrophil infiltration into the widened portal areas were observed in BDL group. Treatment of BDL with HBO attenuated alterations in liver histology. Alpha smooth muscle actin, cytokeratin-positive ductular proliferation, and the activity of terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling in the BDL decreased with HBO treatment.

CONCLUSIONS

The data indicate that HBO attenuates BDL-induced oxidative injury, hepatocytes damage, bile duct proliferation, and fibrosis. The hepatoprotective effect of HBO is associated with antioxidative potential.

Glutamine treatment attenuates endoplasmic reticulum stress and apoptosis in TNBS-induced colitis

Endoplasmic reticulum (ER) stress and apoptotic cell death play an important role in the pathogenesis and perpetuation of inflammatory bowel disease (IBD). We aimed to explore the potential of glutamine to reduce ER stress and apoptosis in a rat model of experimental IBD. Colitis was induced in male Wistar rats by intracolonic administration of 30 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Glutamine (25 mg/dL) was given by rectal route daily for 2 d or 7 d. Both oxidative stress (TBARS concentration and oxidised/reduced glutathione ratio) and ER stress markers (CHOP, BiP, calpain-1 and caspase-12 expression) increased significantly within 48 h of TNBS instillation, and glutamine attenuated the extent of the changes. Glutamine also inhibited the significant increases of ATF6, ATF4 and spliced XBP-1 mRNA levels induced by TNBS instillation. TNBS-colitis resulted in a significant increase in p53 and cytochrome c expression, and a reduced Bcl-xL expression and Bax/Bcl-2 ratio. These effects were significantly inhibited by glutamine. Treatment with the amino acid also resulted in significant decreases of caspase-9, caspase-8 and caspase-3 activities. Double immunofluorescence staining showed co-localization of CHOP and cleaved caspase-3 in colon sections. Phospho-JNK and PARP-1 expression was also significantly higher in TNBS-treated rats, and treatment with glutamine significantly decreased JNK phosphorylation and PARP-1 proteolysis. To directly address the effect of glutamine on ER stress and apoptosis in epithelial cells, the ER stress inducers brefeldin A and tunicamycin were added to Caco-2 cells that were treated with glutamine (5 mM and 10 mM). The significant enhancement in PERK, ATF6 phosphorylated IRE1, BiP and cleaved caspase-3 expression induced by brefeldin A and tunicamycin was partly prevented by glutamine. Data obtained indicated that modulation of ER stress signalling and anti-apoptotic effects contribute to protection by glutamine against damage in TNBS-induced colitis.

Quercetin treatment ameliorates inflammation and fibrosis in mice with nonalcoholic steatohepatitis

We investigated whether quercetin protects from steatosis and limits the expression of proinflammatory and fibrogenic genes in C57BL/6J mice with nonalcoholic steatohepatitis (NASH) induced by feeding a methionine-choline-deficient (MCD) diet. Quercetin (50 mg/kg) was given by oral route daily. Mice were randomly divided into 4 groups that received for 2 or 4 wk: the control diet plus vehicle, control diet plus quercetin, MCD diet plus vehicle, and MCD diet plus quercetin. At both 2 and 4 wk, feeding the MCD diet resulted in liver steatosis, inflammatory cell accumulation, oxidative stress evaluated by the concentration of TBARS, and fibrosis evidenced by the staining of α-smooth muscle actin-positive cells in the liver. At both 2 and 4 wk, the MCD diet induced an increase in the mRNA levels of Il6, Tnf, Ptgs2, and Hmgb1 and increased the protein concentrations of Toll-like receptor-4, c-Jun terminal kinase, and p65 NFκB subunit compared with control rats. Feeding the mice the MCD diet also triggered an increase of Col1a1, Col3a1, Plod3, Tgfb1, Smad3, Smad7, Pdgfb, Ctgf, Areg, Mmp9, and Timp1 mRNA levels. These effects were totally or partially prevented by treatment with quercetin. The data obtained suggest that attenuation of multiple profibrotic and proinflammatory gene pathways contributes to the beneficial effects of quercetin in mice with MCD diet-induced steatohepatitis.

Primary biliary cirrhosis is associated with oxidative stress and endothelial dysfunction but not increased cardiovascular risk

AIM

  Primary biliary cirrhosis (PBC) is a chronic cholestatic disease which is associated with hypercholesterolaemia. Further, cholestatic diseases are associated with deficiencies of anti-oxidant vitamins. Despite these associations PBC is not associated with an increase in cardiovascular mortality. The aim of this study is to assess if primary biliary cirrhosis is associated with oxidative stress, endothelial dysfunction and alteration of vascular compliance which is a surrogate marker for cardiovascular risk.

METHODS

  Fifty-one PBC patients and 34 control subjects were studied. Lipid soluble vitamins A, and E in addition to ascorbate and carotenoids were measured to assess anti-oxidant status. C-reactive protein, hydroperoxides and adhesion molecules sICAM-l/sVCAM-l were assessed as serological measures of endothelial function. Finally, measures of vascular compliance were assessed by applanation tonometer.

RESULTS

  CRP, sICAM and sVCAM were all significantly higher in PBC patients (469.14 vs 207.13, P < 0.001; 768.12 vs 308.03,P < 0.001; 708.40 vs 461.31, P < 0.001) whilst anti-oxidant vitamin levels were lower in PBC patients, with ascorbate, vitamin E and vitamin A all significantly lower in PBC patients (39.91 vs 72.68, P < 0.001; 2.63 vs 3.14, P = 0.02; 1.08 vs 1.81, P < 0.001). Despite these findings PBC patients have a lower pulse wave velocity than control subjects (8.22 m/s vs 8.78 m/s, P = 0.022).

CONCLUSION

  PBC patients appear to have reduced vascular risk as assessed by pulse wave velocity but concurrently have evidence of endothelial dysfunction, inflammation and anti-oxidant deficiency.

The effects of Nigella sativa on bile duct ligation induced-liver injury in rats

Nigella sativa (NS) has been shown to have antioxidant and antiinflammatory activities in different conditions. The goal of this study was to evaluate the effects of NS on cholestatic liver injury in rats. Thirty rats were recruited in the study as follows: Group 1, Bile duct ligation (BDL) (n = 10); Group 2, BDL plus NS (n = 10); and Group 3, Sham (n = 10). Bile duct ligated group received 0.2 mL kg(-1) dose of NS intraperitoneally daily throughout 14 days. Liver damage and cholestasis were determined by the biochemical and the pathologic examination. Data showed a decrease in gamma glutamyl transferase (GGT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activities of the NS treated rats when compared with BDL group (p < 0.001 for GGT and p < 0.05 for others). The NS treated rats' tissue levels of total oxidant status (TOS), oxidative stress index (OSI), and myeloperoxidase (MPO) were significantly lower than that of the BDL group (p < 0.01 for all). Increases in total antioxidant capacity (TAC) and catalase (CAT) levels were statistically significant in the NS treated rats compared to BDL group (p < 0.01 for both). On the other hand, administration of NS in the rats with biliary obstruction resulted in inhibition of necro-inflammation. These results indicate that NS exerts a therapeutic effect on cholestatic liver injury in bile duct ligated rats possibly through attenuation of enhanced neutrophil infiltration and oxidative stress in the liver tissue.

Ethanol-induced liver injury and changes in sulfur amino acid metabolomics in glutathione peroxidase and catalase double knockout mice

BACKGROUND/AIMS

Oxidative stress via generation of reactive oxygen species is suggested to be the major mechanism of alcohol-induced liver injury. We investigated the effects of glutathione peroxidase-1 and catalase double deficiency (Gpx-1(-/-)/Cat(-/-)) on liver injury and changes in the sulfur amino acid metabolism induced by binge ethanol administration.

METHODS

Ethanol (5 g/kg) was administered orally to the wild-type and the Gpx-1(-/-)/Cat(-/-) mice every 12 h for a total of three doses. Mice were sacrificed 6 h after the final dose.

RESULTS

The Gpx-1/Cat deficiency alone increased malondialdehyde levels in liver significantly. Hepatic methionine adenosyltransferase (MAT) activity and S-adenosylmethionine levels were decreased, however, glutathione contents were not changed. Ethanol administration to the Gpx-1(-/-)/Cat(-/-) mice increased the elevation of serum alanine aminotransferase activity, plasma homocysteine levels, hepatic fat accumulation and lipid peroxidation compared with the wild-type animals challenged with ethanol. Also the reduction of MAT activity and S-adenosylmethionine levels was enhanced, but MATI/III expression was increased significantly.

CONCLUSIONS

The results indicate that Gpx-1 and Cat have critical roles in the protection of liver against binge ethanol exposure. Augmentation of ethanol-induced oxidative stress may be responsible for the impairment of the transsulfuration reactions and the aggravation of acute liver injury in the Gpx-1(-/-)/Cat(-/-) mice.

Impaired sulfur-amino acid metabolism and oxidative stress in nonalcoholic fatty liver are alleviated by betaine supplementation in rats

Nonalcoholic fatty liver is involved in the development of nonalcoholic steatohepatitis and chronic liver injury. Impairment of hepatic transsulfuration reactions is suggested to be critically linked with alcoholic liver injury, but its role in nonalcoholic fatty liver remains unknown. We examined the early changes in sulfur-amino acid metabolism and their implication in nonalcoholic fatty liver disease (NAFLD). Male rats were provided with a standard liquid diet or a high-fat liquid diet (HF) for 3 wk. An additional group of rats received the HF diet supplemented with betaine (1%). HF diet intake elevated hepatic triglyceride and serum tumor necrosis factor-alpha (TNFalpha) concentrations. Antioxidant capacity of liver cytosol against hydroxyl and peroxyl radicals was reduced significantly. Hepatic S-adenosylmethionine (SAM) and glutathione (GSH) decreased, but hypotaurine and taurine concentrations increased. Methionine adenosyltransferase (MAT) activity, not its concentration, was depressed, whereas both activity and concentration of cysteine dioxygenase and GSH S-transferase were elevated. Betaine supplementation of the HF diet inhibited hepatic fat accumulation and serum TNFalpha elevation. The decrease in cytosolic antioxidant capacity was also prevented. MAT activity and its concentration were induced significantly. Hepatic SAM and GSH increased and elevation of hypotaurine and taurine was depressed. The results indicate that the metabolism of S-containing substances is significantly disturbed by the HF diet, suggesting a causal role of impairment of hepatic transsulfuration reactions in NAFLD. Betaine supplementation protects the liver from nonalcoholic steatosis and oxidative stress most probably via its effects on the transsulfuration reactions.

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.

Oxidative stress in the development of liver cirrhosis: a comparison of two different experimental models

BACKGROUND/AIMS

Oxidative stress has been implicated in liver cirrhosis. Carbon tetrachloride and thioacetamide are the most widely used models to develop cirrhosis in rats and the present study compares oxidative stress in the liver induced by these compounds at different stages of cirrhosis development.

METHODS

Twice-weekly intragastric or intraperitoneal administration of carbon tetrachloride or thioacetamide, respectively, produced liver cirrhosis after 3 months. Histology, serum markers and hepatic hydroxy proline content confirmed the cirrhosis.

RESULTS

An increase in oxidative stress parameters was seen in mitochondria, peroxisomes and microsomes from the liver after carbon tetrachloride or thioacetamide treatment. Oxidative stress was more severe in carbon tetrachloride treated animals than thioacetamide. Mild oxidative stress was evident at 1 and 2 months of treatment and a significant increase was seen by 3 months of treatment with either compound. By this time, frank liver cirrhosis was also observed.

CONCLUSIONS

These results suggest that evidence of oxygen free radicals is also found early in the development of fibrosis and cirrhosis in both models.

Resveratrol, a red wine constituent polyphenol, protects gastric tissue against the oxidative stress in cholestatic rats

This experimental study was designed to determine the effects of resveratrol on the level of malondialdehyde (MDA), reduced glutathione (GSH), and nitric oxide (NO) in gastric tissue after bile duct ligation (BDL). Swiss albino rats were divided into three groups: Group 1, sham (n = 7); Group 2, BDL (BDL only group; n = 7); and Group 3, BDL plus resveratrol (n = 7). Animals in the resveratrol group were treated with 10 mg/kg resveratrol (i.p.) once a day throughout 28 days. In the resveratrol group, levels of MDA and NO in gastric tissue were significantly lower than in the BDL-only group (P < 0.001). The level of GSH in the resveratrol group was significantly higher than in the BDL-only group (P < 0.001). The present study demonstrates that intraperitoneal administration of resveratrol maintains antioxidant defenses and reduces oxidative gastric damage. This effect of resveratrol may be useful to preserve gastric tissue under oxidative stress due to cholestasis.

Phenylalanine breath test as a method to evaluate hepatic dysfunction in obstructive jaundice

BACKGROUND

The purpose of this study was to investigate whether the hepatic dysfunction associated with obstructive jaundice can be measured from changes in expiratory 13CO2 levels after intravenous administration of l-[1-(13)C]phenylalanine, using a rat model of obstructive jaundice.

MATERIALS AND METHODS

Under pentobarbital anesthesia, bile duct ligation (BDL) was performed (n=12). In the control group, simple laparotomy was performed (n=12). On postoperative day 7, 20 mg/kg l-[1-(13)C]phenylalanine was administered via the femoral vein. Phenylalanine breath test (PBT) was performed for 30 min. We compared single point of 13CO2 level (SPT: T: min) and sum of 13CO2 output (ST) values between BDL and control rats. We examined the correlation of SPT or ST with phenylalanine hydroxylase activity (PHA) and blood chemical parameters.

RESULTS

Both SPT and ST values decreased in BDL compared to control 3 min after the start of PBT (SP10; 103+/-12 (per thousand) versus 84+/-16 (per thousand) P=0.025). PHA/g liver in BDL was significantly decreased compared to control (40.81+/-4.80 (U) versus 28.93+/-9.60 (U) P=0.008). PHA/g liver was correlated with SPT with correlation coefficient of more than 0.715, 10 min after the start of PBT, and the maximum correlation was at SP20 (r=0.801). Blood chemical parameters were correlated with S15 (total bilirubin, r=-0.717; alkaline phosphatase, r=-0.841; gamma-glutamyl transpeptidase, r=-0.759; alanine aminotransferase, r=-0.776; albumin, r=0.819).

CONCLUSIONS

In the breath test with intravenously l-[1-(13)C]phenylalanine, hepatic dysfunction associated with obstructive jaundice could be measured in a short period.

Protective effect of resveratrol against oxidative stress in cholestasis

BACKGROUND

We investigated the protective role of resveratrol in rat liver injuries induced by chronic biliary obstruction.

MATERIALS AND METHODS

Secondary biliary cirrhosis was induced by bile duct ligation for 28 days. Swiss albino rats were divided into the three following groups: group 1: sham (n = 7); group 2: bile duct ligation (n = 7); group 3: bile duct ligation plus resveratrol (n = 7). Bile duct ligation plus resveratrol group received 10 mg/kg dose of resveratrol intraperitoneally daily for 28 days. Liver damage and cholestasis were determined by the biochemical and the pathologic examination.

RESULTS

The present data showed a decrease in both plasma bilirubin levels and aspartate aminotransferase and alanine aminotransferase levels in the resveratrol-treated rats, when compared with bile duct ligation group (P < 0.05). In the resveratrol-treated rats, tissue levels of malondialdehyde and nitric oxide were significantly lower than that of the bile duct ligation (P < 0.002). The levels of glutathione in resveratrol-treated rats were significantly higher than that in bile duct ligation group (P < 0.004). The levels of interleukin-1alpha, interleukin-6, and tumor necrosis factor-alpha in resveratrol group were significantly lower than that in bile duct ligation group (P < 0.004, P < 0.001, P < 0.001, respectively). Administration of resveratrol in the rats with biliary obstruction resulted in inhibition of ductular proliferation and lymphocytic inflammation.

CONCLUSION

The present study demonstrates that intraperitoneal administration of resveratrol in bile duct ligated rats maintained antioxidant defenses and reduces liver oxidative damage and ductular proliferation. This effect of resveratrol may be useful in the preservation of liver function in cholestasis.

Homocysteine alterations in experimental cholestasis and its subsequent cirrhosis

Homocysteine (Hcy), an intermediate in methionine metabolism, has been proposed to be involved in hepatic fibrogenesis. Impaired liver function can alter Hcy metabolism. The aim of the present study was to determine plasma Hcy alterations in acute obstructive cholestasis and the subsequent biliary cirrhosis. Cholestasis was induced by bile duct ligation and sham-operated and unoperated rats were used as controls. The animals were studied on the days 7th, 14th, 21st and 28th after the operation. Plasma Hcy, cysteine, methionine, nitric oxide (NO) and liver S-adenosyl-methionine (SAM), S-adenosyl-homocysteine (SAH), SAM to SAH ratio and glutathione were measured. Chronic L-NAME treatment was also included in the study. Plasma Hcy concentrations were transiently elevated by the day 14th after bile duct ligation (P < 0.01) and subsequently returned to control levels. Similar relative fluctuations in plasma Hcy were observed in BDL rats after intraperitoneal methionine overload. Plasma methionine, cysteine and nitrite and nitrate were significantly increased after bile duct ligation. SAM to SAH ratio was diminished by the 1st week of cholestasis and remained significantly decreased throughout the study. These events were accompanied by a decrease in GSH to GSSG ratio in the liver. Chronic L-NAME treatment improved SAM to SAH ratio and prevented the elevation of plasma Hcy and methionine (P < 0.05) while couldn't influence the other parameters. In conclusion, this study demonstrates alterations in plasma Hcy and liver SAM and SAH contents in precirrhotic stages and in secondary biliary cirrhosis, for the first time. In addition, we observed that plasma Hcy concentrations in BDL rats follow a distinct pattern of alteration from what has been previously reported in other models of cirrhosis. NO overproduction may contribute to plasma Hcy elevation and liver SAM depletion after cholestasis.

Antioxidant properties of S-adenosyl-L-methionine in Fe(2+)-initiated oxidations

S-Adenosylmethionine (SAM) is protective against a variety of toxic agents that promote oxidative stress. One mechanism for this protective effect of SAM is increased synthesis of glutathione. We evaluated whether SAM is protective via possible antioxidant-like activities. Aerobic Hepes-buffered solutions of Fe2+ spontaneously oxidize and consume O2 with concomitant production of reactive oxygen species and oxidation of substrates to radical products, e.g., ethanol to hydroxyethyl radical. SAM inhibited this oxidation of ethanol and inhibited aerobic Fe2+ oxidation and consumption of O2. SAM did not regenerate Fe2+ from Fe3+ and was not consumed after incubation with Fe2+. SAM less effectively inhibited aerobic Fe2+ oxidation in the presence of competing chelating agents such as EDTA, citrate, and ADP. The effects of SAM were mimicked by S-adenosylhomocysteine, but not by methionine or methylthioadenosine. SAM did not inhibit Fe2+ oxidation by H2O2 and was a relatively poor inhibitor of the Fenton reaction. Lipid peroxidation initiated by Fe2+ in liposomes was associated with Fe2+ oxidation; these two processes were inhibited by SAM. However, SAM did not show significant peroxyl radical scavenging activity. SAM also inhibited the nonenzymatic lipid peroxidation initiated by Fe2+ + ascorbate in rat liver microsomes. These results suggest that SAM inhibits alcohol and lipid oxidation mainly by Fe2+ chelation and inhibition of Fe2+ autoxidation. This could represent an important mechanism by which SAM exerts cellular protective actions and reduces oxidative stress in biological systems.

Ebselen protects against the reduction in levels of drug-metabolizing enzymes in livers of rats with deoxycholic acid-induced liver injury

Ebselen is a seleno-organic compound that inhibits oxidative stress by lipid peroxidation through a glutathione peroxidase-like activity. We studied the effect of ebselen on the expression of hepatic drug-metabolizing enzymes in rats with deoxycholic acid-induced liver injury. Hydrophobic bile acids, such as deoxycholic acid, are known to cause cholestatic liver injury, and it was reported that expression of hepatic cytochrome P-450 (CYP) was reduced by deoxycholic acid administration in rats. Hydrophobic bile acids induce lipid peroxidation in the liver, and this may be one mechanism of the development of liver injury. In the present study, we investigated the effect of ebselen (30 mg/kg/day for 10 days) on rats ingesting deoxycholic acid (1% of diet for 10 days). Deoxycholic acid decreased levels of CYP1A1, 2B1, 2E1 and 3A2 to 34, 58, 62 and 37% of control values, respectively, and increased serum alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities to 1.8 and 8.6 times the levels of controls, respectively. Administration of ebselen with deoxycholic acid prevented the decreases in levels of CYP1A1 and 3A2 (86 and 65% of control, respectively) and the increases in serum ALP and ALT activities (1.4 and 1.9 times of control, respectively) caused by deoxycholic acid. These results indicate that ebselen may have a protective effect against hydrophobic bile acid-induced liver injury.

Hemodynamic effects of Salvia miltiorrhiza on cirrhotic rats

Salvia miltiorrhiza (Sm) administration has been shown to reduce hepatic fibrosis in rats. We investigated the hemodynamic effects of Sm on bile duct ligated (BDL) rats. Hemodynamic, histological, and vascular contractile studies were conducted in rats 4 weeks after bile duct ligation. An aqueous extract of Sm (0.2 g twice per day) or vehicle was administered for 4 weeks to BDL rats. Sm treatment in BDL rats significantly reduced histological grades of fibrosis and ameliorated the portal hypertensive state (including portal venous pressure, superior mesenteric artery blood flow, cardiac index, and total peripheral resistance) as compared with vehicle treatment. Moreover, Sm treatment enhanced the vascular sensitivity of mesenteric arteries to phenylephrine in BDL rats. Sm treatment had no effect on plasma biochemical profiles of either BDL or normal rats. Our results suggest that 4-week Sm treatment ameliorates the portal hypertensive state in BDL rats.Key words: hemodynamics, fibrosis, portal hypertension, vascular contractile response, Salvia miltiorrhiza.

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.

Bile duct ligation and oxidative stress in the rat: effects in liver and kidney

In the liver, seven days of bile duct ligation (BDL) decreases the cytochrome P-450 content and the UDP-glucuronyl transferase activity. Also, a decrease in the water soluble antioxidant mechanism reflected in the activities of the enzymes superoxide dismutase (SOD), catalase and the glutathione peroxidase (GTPx) was found in the liver but not in the kidney. Despite an increase in the amount of the GSH in the liver, increased lipid peroxidation is produced in the BDL rats, as indicated by the levels of malondialdehyde (MDA). The kidney responded in a different way to cholestasis, decreasing only the UDP-glucuronyl transferase activity and increasing the levels of GSH and MDA. In the red blood cells the activity of the antioxidant enzymes SOD, GTPx and catalase and the content of GSH were not modulated by cholestasis. In conclusion, disturbance of the oxidant-antioxidant balance might be responsible for cholestatic liver injury and impaired renal function in BDL rats.

Role of glutathione, lipid peroxidation and antioxidants on acute bile-duct obstruction in the rat

The aim of this work was to evaluate the role of lipid peroxidation and glutathione on liver damage induced by 7-day biliary obstruction in the rat. Male Wistar rats were bile-duct-ligated and divided in groups of 10 animals. Groups received vitamin E (400 IU/rat, p.o., daily) or trolox (50 mg/kg, p.o., daily) or both. Lipid peroxidation increased significantly in the livers of bile-duct-ligated rats. Vitamin E and trolox prevented lipid peroxidation. GSH was oxidized in the BDL group and the GSH/GSSG ratio decreased as a consequence. However, total glutathione content increased in liver and blood indicating a possible induction in de novo synthesis of GSH. Antioxidants preserved the normal GSH/GSSG ratio. Despite the observation that antioxidants verted lipid peroxidation and oxidation of GSH, liver injury (as assessed by serum enzyme activities, bilirubin concentration, liver glycogen content and histology) was not affected by the treatments. These results suggest that drugs that inhibit lipid peroxidation and oxidation of glutathione have no effect on conventional biochemical markers of liver injury and on liver histology of bile-duct-ligated rats for 7 days. It seems more likely that the detergent action of bile salts is responsible for solubilization of plasma membranes and cell death, which in turn may lead to oxidative stress, GSH oxidation and lipid peroxidation.

Ursodeoxycholic acid prevents hepatic cytochrome P450 isozyme reduction in rats with deoxycholic acid-induced liver injury

BACKGROUND/AIMS

Hydrophobic bile acids, such as deoxycholic acid produce cholestatic liver injury. Ursodeoxycholic acid has been shown to be useful in the treatment of cholestatic liver disease.

METHODS

In this study, we investigated the effects of deoxycholic acid or ursodeoxycholic acid (1% of diet, for 14 days) and their combination (1% each) on expression of hepatic cytochrome P450 isozymes, their related enzyme activities and mRNA level in rats.

RESULTS

Adding 1% deoxycholic acid to chow caused a marked increase in serum total bilirubin (47-fold) and total bile acid (8-fold) concentrations and in alkaline phosphatase (2.5-fold, p<0.01) and alanine aminotransferase activities (23.5-fold, p<0.01). Adding the same dose of ursodeoxycholic acid along with the deoxycholic acid mitigated both the rise in serum total bilirubin and bile acid concentrations and that in alkaline phosphatase and alanine aminotransferase activities, although the use of ursodeoxycholic acid alone did not affect any of the above. Feeding 1% deoxycholic acid caused a decrease (48% of control) in total cytochrome P450 content in hepatic microsomes. Addition of 1% ursodeoxycholic acid along with the 1% deoxycholic acid completely prevented the decrease in total cytochrome P450 content. Feeding ursodeoxycholic acid alone did not affect the total cytochrome P450 content. The expression of cytochrome P450 2B1, 2E1, 3A2, 2C6, 2C11 and 4A1 proteins in hepatic microsomes was decreased by deoxycholic acid (44, 51, 23, 59, 30 and 74% of control, respectively). Likewise, the activities of cytochrome P450 2B1 (pentoxyresorufin O-depentylation), 2E1 (aniline p-hydroxylation) and 3A2 (testosterone 6beta-hydroxylation) isozymes and the 3A2 mRNA levels in liver were decreased by deoxycholic acid. Addition of 1% ursodeoxycholic acid to 1% deoxycholic acid also prevented the decrease in these cytochrome P450 proteins, related enzyme activities and mRNA levels in liver.

CONCLUSIONS

These results indicate that, in rats with deoxycholic acid-induced liver injury, ursodeoxycholic acid prevents the decrease in hepatic cytochrome P450 isozymes and suggest that ursodeoxycholic acid is useful for the treatment of liver injury in terms of aiding the normalization of the hepatic drug-metabolizing system.

Lipoic acid prevents development of the hyperdynamic circulation in anesthetized rats with biliary cirrhosis

Chronic bile duct ligation is associated with the development of oxidant injury, biliary cirrhosis, portal hypertension, and a hyperdynamic circulation. We have previously demonstrated that the hyperdynamic circulation in the partial portal vein-ligated rat can be prevented by the administration of N-acetylcysteine. To extend these findings, we have examined the effect of lipoic acid, a thiol-containing antioxidant, on hemodynamics, oxidative stress, and nitric oxide (NO) production in bile duct-ligated (BDL) cirrhotic rats. Lipoic acid was given continuously in drinking water to normal and BDL rats; control rats received ordinary drinking water, and animals were studied at 24 days following surgery. Lipoic acid prevented the development of the hyperdynamic circulation (cardiac index [CI]: 15.7 +/- 2.0 vs. 29.5 +/- 2.1 mL x min-1 x 100 g-1; P <. 05) and significantly attenuated the rise in portal pressure (PP) (12.7 +/- 0.8 vs. 15.2 +/- 0.5 mm Hg; P <.05). Hepatic nitric oxide synthase (NOS) activity and plasma nitrite/nitrate concentration increased significantly following bile duct ligation, and both of these were prevented by lipoic acid. Lipoic acid had no effect on the biochemical or histological parameters of liver function in the cirrhotic group. We conclude that lipoic acid prevents the development of the hyperdynamic circulation in the rat model of biliary cirrhosis, and that this is associated with decreased synthesis of NO.

Monocyte chemotactic protein-1 as a chemoattractant for human hepatic stellate cells

Following liver injury, hepatic stellate cells (HSC) undergo proliferation and migrate into damaged areas in response to chemotactic factors. HSC have been shown to regulate leukocyte trafficking by secreting monocyte chemotactic protein-1 (MCP-1), a chemokine that recruits monocytes and lymphocytes. In this study, we explored whether MCP-1 exerts biological actions on HSC. HSC were isolated from normal human livers, cultured on plastic, and studied in their myofibroblast-like phenotype, and three different cells lines were used. Chemotaxis was measured in modified Boyden chambers. Phosphatidylinositol 3-kinase (PI 3-K) was assayed on phosphotyrosine immunoprecipitates. Exposure of HSC to MCP-1 stimulated migration of HSC in a dose-dependent fashion. Maximal stimulation was obtained with 250 ng/mL MCP-1, which resulted in a 3- to 4-fold stimulation of cell migration. Checkerboard analysis showed that the increase in cell migration was almost completely a result of chemotaxis rather than chemokinesis. In contrast, in quiescent HSC, MCP-1 did not exert any effect on cell migration. In leukocytes, MCP-1 activates the pertussis toxin-sensitive CCR2 receptor. However, transcripts for CCR2 could not be shown in HSC, and pertussis toxin only modestly inhibited MCP-1-induced migration. Exposure of HSC to MCP-1 was associated with an increase in cytosolic calcium concentration, PI 3-K activity, protein tyrosine phosphorylation. Blocking calcium influx or pretreatment of HSC with the PI 3-K inhibitor wortmannin markedly reduced cell migration. This study shows, for the first time, a potential direct profibrogenic action of MCP-1 via HSC chemotaxis. MCP-1-dependent signals in these cells are not transduced by CCR2 and may be mediated by alternative chemokine receptors. (HEPATOLOGY 1999;29:140-148.)

Effect of S-adenosylmethionine versus tauroursodeoxycholic acid on bile acid-induced apoptosis and cytolysis in rat hepatocytes

BACKGROUND

S-adenosylmethionine (SAMe) increases survival in alcoholic liver cirrhosis and may have a beneficial effect in cholestatic liver disease. SAMe repletes glutathione stores and protects tissue from oxygen free radicals. The effect of SAMe on bile acid-induced apoptosis is unknown. In the present study the possible hepatoprotective effect of SAMe was evaluated and compared with that of tauroursodeoxycholic acid (TUDCA).

METHODS

Primary rat hepatocytes treated with glycochenodeoxycholic acid (GCDCA) were used as a model for cholestasis-induced hepatocellular damage, which served to study the effects of SAMe and TUDCA on bile acid-induced apoptosis and cytolysis.

RESULTS

SAMe reduced bile acid-induced apoptosis but did not prevent bile acid-induced cytolysis. Compared with SAMe, TUDCA was more efficient in reducing apoptosis due to toxic bile acids. The combination of SAMe and TUDCA had additive effects in reducing apoptosis.

CONCLUSION

The reduction in bile acid-induced apoptosis by SAMe may represent one of the factors responsible for its beneficial effects in the treatment of liver diseases.

Expression of interleukin-10 by in vitro and in vivo activated hepatic stellate cells

Activated hepatic stellate cells (HSC) participate in matrix remodeling and deposition in liver fibrosis. The present study demonstrates that interleukin (IL)-10 is expressed by HSC upon activation in vitro or in vivo and that autocrine effects of this cytokine include inhibition of collagen production. Culture activation of HSC caused a distinct increase in IL-10 mRNA level compared with freshly isolated quiescent HSC. Treatment of cultured HSC with tumor necrosis factor-alpha, transforming growth factor-beta, or lipopolysaccharide further increased IL-10 mRNA by 2-fold and resulted in the release of IL-10 protein into the medium. HSC isolated from rats after bile duct ligation (BDL) showed prominent increases in IL-10 mRNA (x 100) and protein (x 30) levels at 7 days after BDL, but such induction disappeared in advanced liver fibrosis (19 days after BDL). IL-10 expression correlated positively with mRNA expression of interstitial collagenase and inversely with that of alpha1(I) collagen. Addition of anti-IL-10 IgG to cultured HSC caused enhanced collagen production under a basal or stimulated condition with TGF-beta, tumor necrosis factor-alpha, or lipopolysaccharide. These effects were associated with increased alpha1(I) collagen mRNA and reciprocally reduced collagenase mRNA levels. Co-transfection of HSC with an IL-10 expression vector and collagen reporter genes showed a 40% inhibition of alpha1(I) collagen promoter activity. These results demonstrate that activation of HSC causes enhanced autocrine expression of IL-10 which possesses a negative autoregulatory effect on HSC collagen production mediated at least in part by alpha1(I) collagen transcriptional inhibition and stimulation of collagenase expression. These findings, along with the demonstrated early induction of HSC IL-10 expression and its late disappearance during biliary liver fibrosis, suggest its in vivo role in matrix remodeling and a possibility that failure for HSC to sustain IL-10 expression underlies pathologic progression to liver cirrhosis.

Integrin-mediated stimulation of monocyte chemotactic protein-1 expression

We investigated whether activation of integrin receptors could modulate the expression of monocyte chemotactic protein-1 (MCP-1) in human hepatic stellate cells (HSC), mesenchymal cells responsible for extracellular matrix synthesis within the liver. When compared to non-adherent cells, HSC plated on collagen types I or IV, or fibronectin, showed increased MCP-1 gene expression and protein secretion in the conditioned medium. Increased MCP-1 secretion was also observed when cells were plated on dishes coated with a monoclonal antibody directed against the beta1-integrin subunit, demonstrating that ligation of beta1-integrins is sufficient to stimulate MCP-1 expression. Conversely, integrin-independent cell adhesion on poly-L-lysine did not modify MCP-1 secretion. Disruption of the actin cytoskeleton by cytochalasin D blocked the collagen-dependent increase in MCP-1 secretion. Chemotactic assay of HSC-conditioned medium showed that HSC plated on collagen secrete higher amounts of chemotactic factors for lymphomonocytes, and that MCP-1 accounts for the great majority of this effect. These findings indicate a novel mechanism of MCP-1 regulation possibly relevant in those conditions where HSC interact with an altered extracellular matrix.

Antioxidant enzyme status in biliary obstructed rats: effects of N-acetylcysteine

BACKGROUND/AIMS

N-acetylcysteine (NAC) is a modulator of thiol levels that protects against hepatotoxic agents. The aim of this study was to investigate whether NAC might improve hepatic antioxidant defenses in chronically biliary obstructed rats.

METHODS

Secondary biliary cirrhosis was induced by 28 days of bile-duct obstruction. Groups of control and cirrhotic animals received NAC (50 mumol .kg-1.d-1 i.m.) through the experimental period.

RESULTS

Bile-duct obstruction resulted in decreased liver glutathione concentrations. Dichlorofluorescein (DCF) and thiobarbituric acid reactive substances (TBARS) concentrations, measured as markers of production of reactive oxygen species and lipid peroxidation, respectively, were significantly increased. Microsomal and mitochondrial membrane fluidity and the activities of catalase, cytosolic and mitochondrial superoxide dismutase (SOD), glutathione S-transferase, and cytosolic and mitochondrial Se-dependent and Se-independent glutathione peroxidase (GPx) were significantly reduced. NAC corrected the reduction in glutathione concentration and partially prevented the increases in DCF and TBARS concentrations. In addition, NAC treatment resulted in significant preservation of membrane fluidity and of the activities of catalase, mitochondrial SOD and the different forms of GPx.

CONCLUSIONS

Our data indicate that NAC maintains antioxidant defenses in biliary obstructed rats. These effects of NAC suggest that it may be a useful agent to preserve liver function in patients with biliary obstruction.