Oxidative-stress-related changes in the livers of bile-duct-ligated rats

Melatonin and metformin co-loaded nanoliposomes efficiently attenuate liver damage induced by bile duct ligation in rats

In the current study, the therapeutic effectiveness of the metformin (Met) and melatonin (Mel) co-loaded liposomes was investigated on cholestasis induced by bile duct ligation (BDL) in male rats. Histopathological analysis, biochemical analysis, and oxidative stress markers were assayed to determine the therapeutic effect of Met and Mel co-loaded liposomes on cholestasis. Histopathological analysis revealed that the simultaneous administration of Met and Mel, whether in the free (C-Mel-Met) or liposomal (C-Lipo-Mel-Met) forms, reduced inflammation as well as proliferation of bile ducts; however, results were more prominent in the liposomal form of Mel and Met. Additionaly, serum levels of aspartate aminotransferase (AST) were significantly (p < 0.001) higher in (C-Mel-Met) treated rats compared with (BDL) rats; however, (C-Lipo-Mel-Met) treated rats exhibited significant (p < 0.05) lower AST rates in comparison to (BDL) rats. Moreover, a significant (p < 0.0001) drop in bilirubin levels was detected in (C-Lipo-Mel-Met) treated rats in comparison to (BDL) rats; it is noteworthy mentioning that bilirubin levels in (C-Lipo-Mel-Met) treated rats were insignificant in comparison to sham-control (SC) rats. Furthermore, rats concomitantly administered Met and Mel, exhibited significant downregulation in the expression levels of inflammatory cytokine genes such as TNF-α and IL-1 gene expression, where the downregulation was more prominent in the liposomal from. Our findings demonestrate that the concomitant administration of metformin and melatonin in the liposomal form had more therapeutic effect on liver injury than their free forms through improving histological changes, reducing biochemical markers and favoring oxidant- antioxidant balance.

Integrated spatially resolved metabolomics and network toxicology to investigate the hepatotoxicity mechanisms of component D of Polygonum multiflorum Thunb

ETHNOPHARMACOLOGICAL RELEVANCE

The liver toxicity of Reynoutria multiflora (Thunb.) Moldenke. (Polygonaceae) (Polygonum multiflorum Thunb, PM) has always attracted much attention, but the related toxicity materials and mechanisms have not been elucidated due to multi-component and multi-target characteristics. In previous hepatotoxicity screening, different components of PM were first evaluated and the hepatotoxicity of component D [95% ethanol (EtOH) elution] in a 70% EtOH extract of PM (PM-D) showed the highest hepatotoxicity. Furthermore, the main components of PM-D were identified and their hepatotoxicity was evaluated based on a zebrafish embryo model. However, the hepatotoxicity mechanism of PM-D is unknown.

AIM OF THE STUDY

This work is to explore the hepatotoxicity mechanisms of PM-D by integrating network toxicology and spatially resolved metabolomics strategy.

MATERIALS AND METHODS

A hepatotoxicity interaction network of PM-D was constructed based on toxicity target prediction for eight key toxic ingredients and a hepatotoxicity target collection. Then the key signaling pathways were enriched, and molecular docking verification was implemented to evaluate the ability of toxic ingredients to bind to the core targets. The pathological changes of liver tissues and serum biochemical assays of mice were used to evaluate the liver injury effect of mice with oral administration of PM-D. Furthermore, spatially resolved metabolomics was used to visualize significant differences in metabolic profiles in mice after drug administration, to screen hepatotoxicity-related biomarkers and analyze metabolic pathways.

RESULTS

The contents of four key toxic compounds in PM-D were detected. Network toxicology identified 30 potential targets of liver toxicity of PM-D. GO and KEGG enrichment analyses indicated that the hepatotoxicity of PM-D involved multiple biological activities, including cellular response to endogenous stimulus, organonitrogen compound metabolic process, regulation of the apoptotic process, regulation of kinase, regulation of reactive oxygen species metabolic process and signaling pathways including PI3K-Akt, AMPK, MAPK, mTOR, Ras and HIF-1. The molecular docking confirmed the high binding activity of 8 key toxic ingredients with 10 core targets, including mTOR, PIK3CA, AKT1, and EGFR. The high distribution of metabolites of PM-D in the liver of administrated mice was recognized by mass spectrometry imaging. Spatially resolved metabolomics results revealed significant changes in metabolic profiles after PM-D administration, and metabolites such as taurine, taurocholic acid, adenosine, and acyl-carnitines were associated with PM-D-induced liver injury. Enrichment analyses of metabolic pathways revealed tht linolenic acid and linoleic acid metabolism, carnitine synthesis, oxidation of branched-chain fatty acids, and six other metabolic pathways were significantly changed. Comprehensive analysis revealed that the hepatotoxicity caused by PM-D was closely related to cholestasis, mitochondrial damage, oxidative stress and energy metabolism, and lipid metabolism disorders.

CONCLUSIONS

In this study, the hepatotoxicity mechanisms of PM-D were comprehensively identified through an integrated spatially resolved metabolomics and network toxicology strategy, providing a theoretical foundation for the toxicity mechanisms of PM and its safe clinical application.

Empagliflozin Exhibits Hepatoprotective Effects Against Bile Duct Ligation-induced Liver Injury in Rats: A Combined Molecular Docking Approach to In Vivo Studies

BACKGROUND

Cholestatic liver damage is a chronic disease caused by dysfunction of the hepaticbiliary system. Oxidative stress and inflammation are essential factors in the pathogenesis of cholestasis. Thus, the current study was designed to examine the effect of empagliflozin on bile duct ligation-induced liver damage in rats.

METHODS

This study was done on male Wistar rats, which were randomly assigned to the four experimental groups: sham control (SC), bile duct ligation (BDL), SC plus empagliflozin (SC+EMPA) (receiving 10 mg of EMPA orally for 7 days), BDL plus empagliflozin 10 mg/kg (BDL+ EMPA). At the end of the study, the rats were sacrificed, and serum and tissue samples were collected to analyze biochemical parameters, biomarkers of oxidative stress, inflammatory markers, and histopathological changes. The molecular docking technique was performed to elucidate the interaction of EMPA and Cu/Zn-superoxide dismutase (SOD1).

RESULTS

The results showed that BDL elevated the serum activity of ALT, AST, ALP, and levels of TBIL and TPro. BDL also intensifies the oxidative stress state in rats, which was confirmed by augmenting lipid peroxidation (MDA), protein oxidation (PCO), and altering antioxidant defense parameters through decreased SOD, catalase (CAT), and glutathione peroxidase (GPX) levels. Furthermore, the histopathological changes in the liver demonstrated the aggravation of inflammation and oxidative stress. In contrast, treatment with EMPA has shown anti-inflammatory and anti-oxidant effects by reducing TNF-α and IL-6 pro-inflammatory marker proteins, restoring the antioxidant status (increased SOD and GPX), reducing ALT, AST, ALP, TBIL levels, and protein oxidation, and improving the histopathological alterations through reducing bile duct proliferation, fibrosis, focal and portal inflammation. According to the attained findings, the SOD1 activity can be regulated by the EMPA. Our documentation presents direct evidence at the molecular level related to the ability of EMPA to exert its antioxidant performance through certain measures in a particular molecular route.

CONCLUSION

The results showed EMPA to have hepatic protective effects in rats against cholestatic liver injury, an effect mediated by its antioxidant and anti-inflammatory properties.

Dietary Arginine Supplementation Improves Intestinal Mitochondrial Functions in Low-Birth-Weight Piglets but Not in Normal-Birth-Weight Piglets

Our previous studies revealed that _L-arginine supplementation had beneficial effects on intestinal barrier functions of low-birth-weight (LBW) piglets, which were associated with the enhanced antioxidant capacity. Moreover, mitochondrial functions are closely related to the redox state. This study was to explore potential mechanisms of _L-arginine-induced beneficial effects against intestinal dysfunction by regulating mitochondrial function of LBW piglets. Twenty 4-day-old normal birth weight (NBW) piglets (BW: 2.08 ± 0.09 kg) and 20 LBW siblings (BW: 1.16 ± 0.07 kg) were artificially fed either a basal diet or a basal diet supplemented with 1.0% _L-arginine for 21 d, respectively. Growth performance, intestinal morphology, redox status, mitochondrial morphology, and mitochondrial functions were examined. Data were subjected to two-way analysis of variance. LBW piglets presented lower (p < 0.05) ADG, shorter (p < 0.05) intestinal villus height, lower (p < 0.05) jejunal adenosine triphosphate (ATP) content and higher (p < 0.05) concentrations of Ca²⁺ and 8-OH-dG in jejunal mitochondria, compared with NBW piglets. Supplementation with 1.0% _L-arginine significantly increased (p < 0.05) ADG, the activities of CAT, SOD, and GPx, intestinal villus height and mRNA abundances of ZO-1 (2-fold) in the jejunum of LBW piglets, but not in NBW piglets. Furthermore, the concentrations of ATP and the transcription of COX IV, COX V genes were up-regulated (p < 0.05) and the concentration of Ca²⁺ and 8-OH-dG were decreased (p < 0.05) in arginine-treated LBW piglets. The results suggest that mitochondrial morphology is affected, and mitochondrial functions are impaired in the jejunum of LBW piglets. While supplementation with 1.0% _L-arginine relieved intestinal dysfunction through enhancing antioxidant capacity and improving mitochondrial functions via repairing mitochondrial morphology, normalizing mitochondrial calcium, and increasing ATP concentration in the jejunum of LBW piglets. However, supplementation with _L-arginine has no significant beneficial effects on intestinal health in NBW piglets.

Liposome Extract of Stachys pilifera Benth Effectively Improved Liver Damage due to Bile Duct Ligation Rats

Herbal medicines harbor essential therapeutic agents for the treatment of cholestasis. In this study, we have assessed the anticholestatic potential of Stachys pilifera Benth's (SPB's) hydroalcoholic extract encapsulated into liposomes using bile duct ligation- (BDL-) induced hepatic cholestasis in rats. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), malondialdehyde (MDA), total thiol (T-SH) content, protein carbonyl (PCO), total bilirubin (TBIL), albumin (ALB), and nitric oxide (NO) metabolite levels were measured in either liver tissue or plasma to assess liver damage. Moreover, expression of proinflammatory cytokines (IL-1β and TNF-α) and liver fibrosis markers (TGF-β and SM-α) which are driving forces of many liver disorders was also determined. The activity of AST, ALT, and ALP was significantly enhanced in the BDL group in comparison to the control group; however, treatment with liposomal (SPB) hydroalcoholic extract significantly reduced AST and ALT's activity. Increases in MDA, TBIL, and NO levels and T-SH content due to BDL were restored to control levels by liposomal (SPB) hydroalcoholic extract treatment. Similarly, hepatic and plasma oxidative marker MDA levels, significantly enhanced by BDL, were significantly decreased by liposomal (SPB) hydroalcoholic extract treatment. Moreover, histopathological findings further demonstrated a significant decrease in hepatic damage in the liposomal (SPB) hydroalcoholic extract-treated BDL group. In addition, liposomal (SPB) hydroalcoholic extract treatment decreased the liver expression of inflammatory cytokines (IL-1β, TNF-α) and liver fibrosis markers (TGF-β and SM-α). Since liposomal (SPB) hydroalcoholic extract treatment alleviated the BDL-induced injury of the liver and improved the hepatic structure and function more efficiently in comparison to free SPB hydroalcoholic extract, probable liposomal (SPB) hydroalcoholic extract exhibits required potential therapeutic value in protecting the liver against BDL-caused oxidative injury.

Ameliorative effect of vitamins (E and C) on biochemical alterations induced by sublethal concentrations of zinc oxide bulk and nanoparticles in Oreochromis niloticus

The comparison between bulk and nano ZnO particles were antecedently studied but describing the dose-dependent toxicity and the ameliorative effect of vitamins (E and C) in Oreochromis niloticus, have not been previously documented. Therefore, the present study was designed to investigate the ameliorative effect of vitamins (E and C) against oxidative stress and biochemical alterations induced by sublethal concentrations of zinc oxide bulk particles (ZnOBPs) and zinc oxide nanoparticles (ZnONPs). Toxicity tests were carried out on O. niloticus and showed that 96 h LC₅₀ values of ZnOBPs and ZnONPs were 84 mg/l and 5.6 mg/l respectively. Exposure of the studied fish to these sublethel concentrations for 7, 14, 21 & 28 days showed a significant increase (p < 0.05) in serum glucose, AST, ALT, creatinine, urea and uric acid compared to control groups while, fish groups exposed to ZnOBPs or ZnONPs and supplemented with vitamins E and C, their serum enzyme concentrations were decreased compared to the groups without supplementation after 7, 14, 21 and 28 day. On the other hand, antioxidant defense enzymes (SOD, CAT and GST) activity in O.niloticus fish were increased significantly (p < 0.05) when exposed to sublethal concentrations of ZnOBPs or ZnONPs compared to the control value. However, fish groups supplemented with vitamins (E and C) have a decrease in SOD, CAT and GST enzymes activity when compared to unsupplemented groups and the values returned to similar levels established in the control at low concentrations but still higher than control at the high concentrations.

Effect of bile duct ligation-induced liver dysfunction on methamphetamine pharmacokinetics in male and female rats

BACKGROUND

Several disease states commonly associated with methamphetamine (METH) use produce liver dysfunction, and in the bile duct ligation (BDL) model of hepatic dysfunction, rats with liver injury are more sensitive to METH effects. Additionally, both female rats and humans are known to be more sensitive to METH than males. In consideration of known sex-dependent differences in METH pharmacokinetics, this study sought to determine the potential interaction between sex and liver dysfunction variables on METH pharmacokinetics.

METHODS

Sham or BDL surgery was performed on male and female rats on day 0. Serum biomarker and pharmacokinetics studies with 3 mg/kg subcutaneous (SC) METH were performed on day 7. METH-induced weight loss was measured on day 8. Liver histology evaluation and brain METH concentration measurements were performed on day 9.

RESULTS

While BDL surgery produced significantly elevated alanine aminotransferase and bile duct proliferation in male compared to female rats, there were no significant interactions between sex and liver function in the pharmacokinetic parameters. Both liver dysfunction and female sex, however, were associated with significantly slower METH serum clearance and significantly higher brain METH concentrations (p < .05).

CONCLUSIONS

BDL-induced hepatic dysfunction produces substantial reductions in METH clearance and increased brain METH concentrations in both male and female rats, despite less liver injury in females. This preclinical model may be useful to identify and correct potential liver dysfunction comorbidity-related problems with future pharmacotherapy for stimulant use disorder with METH prior to expensive clinical trials.

Impact of liver damage on blood-borne variables and pulmonary hemodynamic responses to hypoxia and hyperoxia in anesthetized rats

BACKGROUND

Liver disorders may be associated with normal pulmonary hemodynamic, hepatopulmonary syndrome (HPS), or portopulmonary hypertension (POPH). In this study, we aimed to investigate the effect of the severity of liver dysfunctions on blood-borne variables, and pulmonary hemodynamic during repeated ventilation with hyperoxic and hypoxic gases.

METHODS

Female Sprague Dawley rats were assigned into four groups of Sham (n = 7), portal vein ligation (PPVL, n = 7), common bile duct ligation (CBDL, n = 7), and combination of them (CBDL+ PPVL, n = 7). Twenty-eight days later, right ventricular systolic pressure (RVSP) and systemic blood pressure were recorded in anesthetized animals subjected to repeated maneuvers of hyperoxia (O₂ 50%) and hypoxia (O₂ 10%). Besides, we assessed blood parameters and liver histology.

RESULTS

Liver histology score, liver enzymes, WBC and plasma malondialdehyde in the CBDL+PPVL group were higher than those in the CBDL group. Also, the plasma platelet level in the CBDL+PPVL group was lower than those in the other groups. On the other hand, the serum estradiol in the CBDL group was higher than that in the CBDL+PPVL group. All the above parameters in the PPVL group were similar to those in the Sham group. During ventilation with hyperoxia gas, RVSP in the CBDL+PPVL group was higher than the ones in the other groups, and in the CBDL group, it was more than those in the PPVL and Sham groups. Hypoxic pulmonary vasoconstriction (HPV) was not detected in both CBDL+PPVL and CBDL groups, whereas, it retained in the PPVL group.

CONCLUSION

Severe liver damage increases RVSP in the CBDL+PPVL group linked to the high level of ROS, low levels of serum estradiol and platelets or a combination of them. Furthermore, the high RVSP at the noted group could present a reliable animal model for POPH in female rats.

Hepatoprotective effect of sodium hydrosulfide on hepatic encephalopathy in rats

Hydrogen sulfide is well-known to exhibit anti-inflammatory and cytoprotective activities, and also has protective effects in the liver. This study aimed to examine the protective effect of hydrogen sulfide in rats with hepatic encephalopathy, which was induced by mild bile duct ligation. In this rat model, bile ducts were mildly ligated for 26 days. Rats were treated for the final 5 days with sodium hydrosulfide (NaHS). NaHS (25 µmol/kg), 0.5% sodium carboxymethyl cellulose, or silymarin (100 mg/kg) was administered intraperitoneally once per day for 5 consecutive days. Mild bile duct ligation caused hepatotoxicity and inflammation in rats. Intraperitoneal NaHS administration reduced levels of aspartate aminotransferase and alanine aminotransferase, which are indicators of liver disease, compared to levels in the control mild bile duct ligation group. Levels of ammonia, a major causative factor of hepatic encephalopathy, were also significantly decreased. Malondialdehyde, myeloperoxidase, catalase, and tumor necrosis factor-α levels were measured to confirm antioxidative and anti-inflammatory effects. N-Methyl-D-aspartic acid (NMDA) receptors with neurotoxic activity were assessed for subunit NMDA receptor subtype 2B. Based on these data, NaHS is suggested to exhibit hepatoprotective effects and guard against neurotoxicity through antioxidant and anti-inflammatory actions.

Glutamine prevents oxidative stress in a model of portal hypertension

AIM

To evaluate the protective effects of glutamine in a model of portal hypertension (PH) induced by partial portal vein ligation (PPVL).

METHODS

Male Wistar rats were housed in a controlled environment and were allowed access to food and water ad libitum. Twenty-four male Wistar rats were divided into four experimental groups: (1) control group (SO) - rats underwent exploratory laparotomy; (2) control + glutamine group (SO + G) - rats were subjected to laparotomy and were treated intraperitoneally with glutamine; (3) portal hypertension group (PPVL) - rats were subjected to PPVL; and (4) PPVL + glutamine group (PPVL + G) - rats were treated intraperitoneally with glutamine for seven days. Local injuries were determined by evaluating intestinal segments for oxidative stress using lipid peroxidation and the activities of glutathione peroxidase (GPx), endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) after PPVL.

RESULTS

Lipid peroxidation of the membrane was increased in the animals subjected to PH (P < 0.01). However, the group that received glutamine for seven days after the PPVL procedure showed levels of lipid peroxidation similar to those of the control groups (P > 0.05). The activity of the antioxidant enzyme GTx was decreased in the gut of animals subjected to PH compared with that in the control group of animals not subjected to PH (P < 0.01). However, the group that received glutamine for seven days after the PPVL showed similar GTx activity to both the control groups not subjected to PH (P > 0.05). At least 10 random, non-overlapping images of each histological slide with 200 × magnification (44 pixel = 1 μm) were captured. The sum means of all areas, of each group were calculated. The mean areas of eNOS staining for both of the control groups were similar. The PPVL group showed the largest area of staining for eNOS. The PPVL + G group had the second highest amount of staining, but the mean value was much lower than that of the PPVL group (P < 0.01). For iNOS, the control (SO) and control + G (SO + G) groups showed similar areas of staining. The PPVL group contained the largest area of iNOS staining, followed by the PPVL + G group; however, this area was significantly smaller than that of the group that underwent PH without glutamine (P < 0.01).

CONCLUSION

Treatment with glutamine prevents gut mucosal injury after PH in rats.

Quercetin protects liver injury induced by bile duct ligation via attenuation of Rac1 and NADPH oxidase1 expression in rats

BACKGROUND

Bile duct ligation (BDL) and subsequent cholestasis are correlated with oxidative stress, hepatocellular injury and fibrosis. Quercetin is a flavonoid with antifibrotic, and hepatoprotective properties. However, the molecular mechanism underlying quercetin-mediated hepatoprotection is not fully understood. The current study was to evaluate mechanisms of hepatoprotective effect of quercetin in BDL rat model.

METHODS

We divided male Wistar rats into 4 groups (n=8 for each): sham, sham+quercetin (30 mg/kg per day), BDL, and BDL+quercetin (30 mg/kg per day). Four weeks later, the rats were sacrificed, the blood was collected for liver enzyme measurements and liver for the measurement of Rac1, Rac1-GTP and NOX1 mRNA and protein levels by quantitative PCR and Western blotting, respectively.

RESULTS

Quercetin significantly alleviated liver injury in BDL rats as evidenced by histology and reduced liver enzymes. Furthermore, the mRNA and protein expression of Rac1, Rac1-GTP and NOX1 were significantly increased in BDL rats compared with those in the sham group (P<0.05); quercetin treatment reversed these variables back toward normal (P<0.05). Another interesting finding was that the antioxidant markers e.g. superoxide dismutase and catalase were elevated in quercetin-treated BDL rats compared to BDL rats (P<0.05).

CONCLUSION

Quercetin demonstrated hepatoprotective activity against BDL-induced liver injury through increasing antioxidant capacity of the liver tissue, while preventing the production of Rac1, Rac1-GTP and NOX1 proteins.

Cholestatic liver injury model of bile duct ligation and the protection of Huang-Lian-Jie-Du decoction by NMR metabolomic profiling

Bile duct ligation (BDL) induced cholestasis in rats and the treatment effects of Huang-Lian-Jie-Du decoction (HLJDD) were investigated by NMR-based metabolomics approach: biphasic feature of BDL model and bilateral adjustment of HLJDD were found.

Royal jelly attenuates azathioprine induced toxicity in rats

In the present study, we investigated the potential protective effects of royal jelly against azathioprine-induced toxicity in rat. Intraperitoneal administration of azathioprine (50 mg/kgB.W.) induced a significant decrease in RBCs count, Hb concentration, PCV%, WBCs count, differential count and platelet count, hepatic antioxidant enzymes (reduced glutathione and glutathione s-transferase) and increase of serum transaminases (alanine aminotransferase and aspartate aminotransferase enzymes) activities, alkaline phosphatase and malondialdehyde formation. Azathioprine induced hepatotoxicity was reflected by marked pathological changes in the liver. Oral administration of royal jelly (200 mg/kgB.W.) was efficient in counteracting azathioprine toxicity whereas it altered the anemic condition, leucopenia and thrombocytopenia induced by azathioprine. Furthermore, royal jelly exerted significant protection against liver damage induced by azathioprine through reduction of the elevated activities of serum hepatic enzymes. Moreover, royal jelly blocked azathioprine-induced lipid peroxidation through decreasing the malondialdehyde formation. In conclusion, royal jelly possesses a capability to attenuate azathioprine-induced toxicity.

Activity of glycogen synthase and glycogen phosphorylase in normal and cirrhotic rat liver during glycogen synthesis from glucose or fructose

Cirrhotic patients often demonstrate glucose intolerance, one of the possible causes being a decreased glycogen-synthesizing capacity of the liver. At the same time, information about the rates of glycogen synthesis in the cirrhotic liver is scanty and contradictory. We studied the dynamics of glycogen accumulation and the activity of glycogen synthase (GS) and glycogen phosphorylase (GP) in the course of 120min after per os administration of glucose or fructose to fasted rats with CCl4-cirrhosis or fasted normal rats. Blood serum and liver pieces were sampled for examinations. In the normal rat liver administration of glucose/fructose initiated a fast accumulation of glycogen, while in the cirrhotic liver glycogen was accumulated with a 20min delay and at a lower rate. In the normal liver GS activity rose sharply and GPa activity dropped in the beginning of glycogen synthesis, but 60min later a high synthesis rate was sustained at the background of a high GS and GPa activity. Contrariwise, in the cirrhotic liver glycogen was accumulated at the background of a decreased GS activity and a low GPa activity. Refeeding with fructose resulted in a faster increase in the GS activity in both the normal and the cirrhotic liver than refeeding with glucose. To conclude, the rate of glycogen synthesis in the cirrhotic liver is lower than in the normal one, the difference being probably associated with a low GS activity.

Vitamin E inhibits hepatic oxidative stress, toxicity and hyperproliferation in rats treated with the renal carcinogen ferric nitrilotriacetate

Ferric nitrilotriacetate (Fe-NTA) is a potent renal and hepatic tumor promoter, which acts through a mechanism involving oxidative stress. Fe-NTA when injected intraperitoneally into rats induces hepatic ornithine decarboxylase activity as well as hepatic DNA synthesis. Vitamin E is a well-known, lipid-soluble and chain-breaking antioxidant which protects cell membranes from peroxidative damage. In this study, we investigated the protective effect of vitamin E, a major fat-soluble antioxidant, against Fe-NTA-mediated hepatic oxidative stress, toxicity and hyperproliferation in Wistar rats. Animals were treated with two different doses of vitamin E for 1 week prior to Fe-NTA treatment. Vitamin E at a higher dose of 2.0 mg/animal/day showed significant reduction in Fe-NTA-induced hepatic ornithine decarboxylase activity, DNA synthesis, microsomal lipid peroxidation and hydrogen peroxide generation. Fe-NTA treatment alone caused depletion of glutathione, glutathione metabolizing and antioxidant enzymes in rat liver, whereas pretreatment of animals with vitamin E reversed these changes in a dose-dependent manner. Taken together, our results suggest that vitamin E may afford substantial protection against the damage caused by Fe-NTA exposure and can serve as a potent preventive agent to suppress oxidant-induced tissue injury.

Sex differences of oxidative stress to cholestatic liver and kidney injury in young rats

BACKGROUND

Sexual dimorphism plays a role in the liver and in renal injuries. However, whether sex is a risk factor in bile duct ligation (BDL) in young rats has never been examined.

METHODS

Six male and six female rats treated with BDL were sacrificed 2 weeks after surgery and were designated as BDL-M and BDL-F groups. The other six male and six female rats that received sham ligation were designated as sham-M and sham-F groups. Plasma biochemistry and liver and kidney asymmetric dimethylarginine (ADMA)-related molecules were examined.

RESULTS

Both BDL-M and BDL-F groups had elevated plasma aspartate transaminase (AST), alanine transaminase (ALT), bilirubin, and transforming growth factor-β1 levels. The BDL-F group had lower plasma AST and ALT levels than the BDL-M group. The BDL-M and BDL-F groups had elevated plasma ADMA levels. The cationic amino acid transporter 1 (CAT1) level was increased in the BDL-F group as compared to the sham-F group, whereas the CAT2 level was reduced in the both BDL-M and BDL-F groups.

CONCLUSION

We found that young male rats were prone to higher degrees of biochemical liver and kidney injury to cholestasis. Sex differences in modulation of oxidative stress markers, such as ADMA, may play a role. Our results support careful monitoring and optimal treatment of cholestatic disease, especially in young male patients.

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.

Cholestasis is associated with hepatic microvascular dysfunction and aberrant energy metabolism before and during ischemia-reperfusion

AIMS

The aim was to investigate the impact of ischemia-reperfusion (I/R) on intrahepatic oxidative stress, oxidative phosphorylation, and nucleotide metabolism in relation to liver damage and inflammation in cholestatic rats to elucidate the molecular mechanisms responsible for post-I/R pathogenesis during cholestasis.

RESULTS

Pre-I/R cholestatic livers exhibited mild hepatopathology in the form of oxidative/nitrosative stress, perfusion defects, necrosis and apoptosis, inflammation, and fibrosis. Plasma bilirubin concentration in cholestatic livers was 190 μM. I/R in cholestatic livers exacerbated hepatocellular damage and leukocyte infiltration. However, myeloperoxidase activity in neutrophils at 6 h reperfusion was not elevated in cholestatic livers compared to pre-I/R levels and to control (Ctrl) livers. At 6 h reperfusion, cholestatic livers exhibited severe histological damage, which was absent in Ctrl livers. Despite a lower antioxidative capacity after I/R, no cardiolipin peroxidation and equivalent reduced glutathione/oxidized glutathione ratios and Hsp70 levels were found in cholestatic livers versus Ctrls. Bilirubin acted as a potent and protective antioxidant. Postischemic resumption of oxidative phosphorylation in Ctrl livers proceeded rapidly and encompassed reactive hyperemia, which was significantly impaired in cholestatic livers owing to extensive vasoconstriction and perfusion defects. Normalization of intrahepatic energy status and nucleotide-based metabolic cofactors was delayed in cholestatic livers during reperfusion. Innovation and

CONCLUSIONS

Cholestatic livers possess sufficient antioxidative capacity to ameliorate radical-mediated damage during I/R. I/R-induced damage in cholestatic livers is predominantly caused by microvascular perfusion defects rather than exuberant oxidative/nitrosative stress. The forestalled rate of oxidative phophorylation and recovery of bioenergetic and possibly metabolic parameters during the early reperfusion phase are responsible for extensive liver damage.

The effect of ursodeoxycholic acid on oxidative stress level and DNase activity in rat liver after bile duct ligation

Accumulation of hydrophobic bile acids (BAs) during cholestasis plays an important role in apoptosis initiation as well as oxidative stress increase in liver cells. Ursodeoxycholic acid (UDCA) acts as a protector in BA-induced cell injury.The aim of the study was to evaluate the effect of UDCA on oxidative stress level and DNase I and II activity caused by liver injury in bile duct ligation (BDL) rats.Wistar rats were divided in four groups: group 1, control (sham-operated); group 2, sham-operated and injected with UDCA (30 mg/kg); group 3,animals with BDL; and group 4,UDCA-treatedcholestatic rats. Animals were sacrificed after 9 days. Malondialdehyde (MDA; lipid peroxidation end-product) level and protein-molecule oxidative modification (carbonyl group content) significantly increased in BDL rat liver. Catalase (CAT) activity in liver tissue was found to be decreased in BDL rats. In addition, xanthine oxidase (XO) activity, which is thought to be one of the key enzymes producing reactive oxygen species, was found to be increased in the cholestatic group. The apoptotic effect in cholestasis was probably triggered by the increased activation of DNase I and II. The protective effect of UDCA on liver tissue damage in BDL rats, in comparison to cholestatic liver, were 1) decrease of MDA levels, 2) increased CAT activity, 3) reduced XO activity, and 4) effect on terminal apoptotic reaction, shown as a decrease in DNase I and II activity.Therefore, UDCA may be useful in the preservation of liver function in cholestasis treatment.

Therapeutic effect of captopril, pentoxifylline, and cordyceps sinensis in pre-hepatic portal hypertensive rats

BACKGROUND/AIM

Portal hypertension is an important and potentially fatal complication of liver disease whereby cellular and fibrotic alterations manifest to increase portal venous pressure. The aim of this study is to investigate the effect of captopril, pentoxifylline (PTX), and cordyceps sinensis in pre-hepatic portal hypertensive rats.

SETTINGS AND DESIGN

Wistar male rats were divided at random into 3 main groups: the first group: control rats. The second group: sham-operated rats and the third group: prehepatic portal hypertensive rats (PHPHT) induced by regulated pre-hepatic portal vein ligation. After 14 days, Group 3 was subdivided into 5 subgroups. Subgroup (1): portal vein-ligated (PVL) was killed at once; Subgroup (2): received distilled water for 30 days (untreated PVL group); subgroups 3-5 were treated with captopril (60 mg/kg, orally); PTX (100 mg/kg, orally); and C. sinensis (200 mg/kg, orally), respectively, as a single daily dose for 30 days.

PATIENTS AND METHODS

Portal pressure, nitric oxide (NO), antioxidant enzymes, Liver enzymes, and creatinine levels were measured to evaluate the status of the liver state.

RESULTS

Portal vein ligation produced significant increments in liver enzymes, NO, creatinine and portal pressure concomitant with significant decrements in glutathione content and superoxide dismutase activity. Treatment with captopril, PTX, and C. sinensis resulted in a significant reduction in liver enzymes, NO, creatinine and portal pressure and observable increase in antioxidant enzymes.

CONCLUSIONS

captopril, PTX, and C. sinensis have promising effect in controlling PHPHT and reducing hyperdynamic circulatory state through reduction of portal pressure and NO level.

Hepatoprotective and antioxidant effects of licorice extract against CCl₄-induced oxidative damage in rats

Licorice has been used in Chinese folk medicine for the treatment of various disorders. Licorice has the biological capabilities of detoxication, antioxidation, and antiinfection. In this study, we evaluated the antihepatotoxic effect of licorice aqueous extract (LE) on the carbon tetrachloride (CCl₄)-induced liver injury in a rat model. Hepatic damage, as reveled by histology and the increased activities of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) activities, and decreased levels of serum total protein (TP), albumin (Alb) and globulin (G) were induced in rats by an administration of CCl₄ at 3 mL/kg b.w. (1:1 in groundnut oil). Licorice extract significantly inhibited the elevated AST, ALP and ALT activities and the decreased TP, Alb and G levels caused by CCl₄ intoxication. It also enhanced liver super oxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), Glutathione S-transferase (GST) activities and glutathione (GSH) level, reduced malondialdehyde (MDA) level. Licorice extract still markedly reverses the increased liver hydroxyproline and serum TNF-α levels induced by CCl₄ intoxication. The data of this study support a chemopreventive potential of licorice extract against liver oxidative injury.

Bile duct ligation in developing rats: temporal progression of liver, kidney, and brain damage

PURPOSE

Cholestatic liver disease may result in progressive end-stage liver disease and other extrahepatic complications. We explored the temporal progression of bile duct ligation (BDL)-induced cholestasis in developing rats, focusing on brain cognition and liver and kidney pathology, to elucidate whether these findings were associated with asymmetric dimethylarginine and oxidative stress alterations.

MATERIALS AND METHODS

Three groups of young male Sprague-Dawley rats were studied: one group underwent laparotomy (sham), another group underwent laparotomy and BDL for 2 weeks (BDL2), and a third group underwent laparotomy and BDL for 4 weeks (BDL4).

RESULTS

The effect of BDL on liver was represented by transforming growth factor beta1 levels and histology activity index scores, which were worse in the BDL4 rats than in the BDL2 rats. BDL4 rats also exhibited more severe spatial memory deficits than BDL2 rats. In addition, renal injury was more progressive in BDL4 rats than in BDL2 rats because BDL4 rats displayed higher Cr levels, elevated tubulointerstitial injury scores, neutrophil gelatinase-associated lipocalin, and symmetric dimethylarginine levels.

CONCLUSIONS

Our findings highlight the fact that young BDL rats exhibit similar trends of progression of liver, kidney, and brain damage. Further studies are needed to better delineate the nature of progression of organ damage in young cholestatic rats.

Bile duct ligation: step-by-step to cholangiocyte inflammatory tumorigenesis

Chronic liver inflammation after murine bile duct ligation could evolve according to three interrelated phenotypes, which would have different metabolic, functional and histologic characteristics. Liver injury secondary to extrahepatic cholestasis would induce an early ischemic-reperfusion phenotype with cholangiocyte depolarization, abnormal ion transport, hypometabolism with anaerobic glycolysis and hepatocytic apoptosis. This phenotype, in turn, could trigger the switch to a leukocytic phenotype by the cholangiocytes, with an intense anaplerotic activity, hypermetabolism, extracellular matrix degradation and moderated proliferation to create a pseudotissue with metabolic autonomy and paracrine functions. In the long-term cholestasis-drive tumorigenesis, the tumorous tissue would principally consist of cholangiocyte parenchyma, with an impressive biosynthetic activity through the tricarboxylic cell cycle. In terms of the tumorous stroma, made up by fibroplasia and angiogenesis, it would favor the tumor trophism. In conclusion, the great intensity and persistence in the expression of these phenotypes by the cholestatic cholangiocyte would favor chronic inflammatory tumorigenesis.

Effects of carbon dioxide pneumoperitoneum on hepatic function in obstructive jaundice: an experimental study in a rat model

BACKGROUND AND AIMS

The physiology of the patient during laparoscopy differs from that of open surgery. Both pneumoperitoneum and obstructive jaundice impair the hepatic function, but the combined insult has not been previously examined. In this study, we aimed to investigate the effects of carbon dioxide (CO(2)) pneumoperitoneum on hepatic function in a rat model of obstructive jaundice.

METHODS

Forty-four male Sprague-Dawley rats were divided into four groups: group 1 (n = 10), sham-operated group; group 2 (n = 12), obstructive jaundice group; group 3 (n = 10), CO(2) pneumoperitoneum group; and group 4 (n = 12), obstructive jaundice and CO(2) pneumoperitoneum group. Common bile duct was ligated and divided in the obstructive jaundice groups. After 6 days, a 12-mmHg pneumoperitoneum was induced, maintained for 60 min, and released for 120 min. Blood samples were drawn for the measurement of white blood cell and platelet counts, serum liver enzymes (aspartate aminotransferase [AST], alanine aminotransferase [ALT], total bilirubin). Tissue samples were obtained for analyses of malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) levels. We evaluated the degree of liver injury on a grading scale from 0 to 4, histopathologically.

RESULTS

Pneumoperitoneum after biliary obstruction resulted in an increase in AST and ALT levels and a decrease in white blood cell and platelet counts. However, changes in liver tissue MDA, GSH, and SOD levels did not correlate with the changes in AST and ALT levels and white blood cell and platelet counts. After sham operation with pneumoperitoneum, the GSH levels in liver homogenate were significantly decreased in the group 3 when compared to the group 2. On the other hand, obstructive jaundice itself caused significant reduction in the SOD activity of liver homogenate in comparison to the group 3. Histopathologically, sinusoidal congestion and vacuolization were more severe in the group 3.

CONCLUSIONS

Alterations in hepatic function occur in pneumoperitoneum applied jaundiced subjects. However, there were no statistically significant differences between the groups 2 and 4 with regard to white blood cell and platelet counts, serum liver enzymes including AST, ALT, and total bilirubin values, MDA and GSH levels and SOD activity of liver homogenate, and histologic damage. These results indicate that there is no additional risk on liver function associated with pneumoperitoneum performed in obstructive jaundice.

Inhibitory effects of armepavine against hepatic fibrosis in rats

Activation of hepatic stellate cells (HSCs) plays a crucial role in liver fibrogenesis. armepavine (Arm, C₁₉H₂₃O₃N), an active compound from Nelumbo nucifera, has been shown to exert immunosuppressive effects on T lymphocytes and on lupus nephritic mice. The aim of this study was to investigate whether Arm could exert anti-hepatic fibrogenic effects in vitro and in vivo. A cell line of rat HSCs (HSC-T6) was stimulated with tumor necrosis factor-α (TNF-α) or lipopolysaccharide (LPS) to evaluate the inhibitory effects of Arm. An in vivo therapeutic study was conducted in bile duct-ligated (BDL) rats. BDL rats were given Arm (3 or 10 mg/kg) by gavage twice daily for 3 weeks starting from the onset of BDL. Liver sections were taken for fibrosis scoring, immuno-fluorescence staining and quantitative real-time mRNA measurements. In vitro, Arm (1-10 μM) concentration-dependently attenuated TNF-α- and LPS-stimulated α-SMA protein expression and AP-1 activation by HSC-T6 cells without adverse cytotoxicity. Arm also suppressed TNF-α-induced collagen collagen deposition, NFκB activation and MAPK (p38, ERK1/2, and JNK) phosphorylations. In vivo, Arm treatment significantly reduced plasma AST and ALT levels, hepatic α-SMA expression and collagen contents, and fibrosis scores of BDL rats as compared with vehicle treatment. Moreover, Arm attenuated the mRNA expression levels of col 1α2, TGF-β1, TIMP-1, ICAM-1, iNOS, and IL-6 genes, but up-regulated metallothionein genes. Our study results showed that Arm exerted both in vitro and in vivo antifibrotic effects in rats, possibly through anti-NF-κB activation pathways.

Melatonin ameliorates bile duct ligation-induced systemic oxidative stress and spatial memory deficits in developing rats

Bile duct ligation (BDL) induces primary biliary cirrhosis characterized by cholestasis, impaired liver function, and cognition. Young male Sprague-Dawley rats were used: rats underwent laparotomy without BDL [sham-control (SC) group]; rats had restricted diets supply [diet-control (DC) group]; rats underwent BDL for 2 wk (BDL group); BDL rats with melatonin (500 microg/kg/d) intraperitoneally for 2 wk [melatonin (500 microg/kg/d) (M500) group]; and BDL rats with melatonin (1000 microg/kg/d/intraperitoneally) for 2 wk [melatonin (1000 microg/kg/d) (M1000) group]. All the surviving rats were assessed for spatial memory and blood was tested for biochemical study. Liver, brain cortex, and hippocampus were collected for determination of malondialdehyde (MDA) and glutathione (GSH)/oxidized glutathione (GSSG) ratios. BDL group rats had significantly higher plasma direct/total bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), MDA values and higher liver MDA values and lower GSH/GSSG ratios when compared with SC group. In addition, BDL group rats had impaired spatial performance. After melatonin treatment, cholestatic rats' plasma MDA levels, liver MDA levels, and liver GSH/GSSG ratios approached to the values of SC group. Only high dose of melatonin improved spatial performance. Results of this study indicate cholestasis in the developing rats increase oxidative stress and cause spatial memory deficits, which are prevented by melatonin treatment.

Biliary fibrosis in microsurgical extrahepatic cholestasis in the rat

A new model of extrahepatic cholestasis, using a microsurgical technique, is performed as an alternative to the traditional model of the bile duct ligated-rat, in order to study the stage of fibrosis in the long-term. Male Wistar rats were divided into two groups: I (Sham-operated, n = 9) and II [Microsurgical Cholestasis (MC), n = 10]. After 4 weeks, portal pressure, types of portosystemic collateral circulation, mesenteric venous vasculopathy, hepatic function test, and liver histopathology were studied by using the Knodell index and fibrosis was determined by reticulin and Sirius red stains. The animals with MC presented portal hypertension with extrahepatic portosistemic collateral circulation, associated with mesenteric venous vasculopathy and increased plasma levels of bilirubin (6.30 +/- 1.80 vs. 0.22 +/- 0.37 mg/dL; P = 0.0001), alkaline phosphatase (293.00 +/- 82.40 vs. 126.30 +/- 33.42 U/L; P = 0.001), AST (380.00 +/- 78.50 vs. 68.33 +/- 11.74 IU/L; P = 0.0001), ALT (87.60 +/- 22.32 vs. 42.22 +/- 7.89 IU/L; P = 0.0001), and LDH (697.76 +/- 75.13 vs. 384.80 +/- 100.03 IU/L; P = 0.0001). On the contrary, plasma levels of albumin decreased (2.72 +/- 0.12 mg/dl vs. 2.99 +/- 0.10; P = 0.001). The microsurgical resection of the extrahepatic biliary tract in the rat produces an experimental model of hepatic inflammation, characterized by a high Knodell hepatic activity index (4), bile proliferation, and fibrosis.

Experimental obstructive cholestasis: the wound-like inflammatory liver response

Obstructive cholestasis causes hepatic cirrhosis and portal hypertension. The pathophysiological mechanisms involved in the development of liver disease are multiple and linked. We propose grouping these mechanisms according to the three phenotypes mainly expressed in the interstitial space in order to integrate them.Experimental extrahepatic cholestasis is the model most frequently used to study obstructive cholestasis. The early liver interstitial alterations described in these experimental models would produce an ischemia/reperfusion phenotype with oxidative and nitrosative stress. Then, the hyperexpression of a leukocytic phenotype, in which Kupffer cells and neutrophils participate, would induce enzymatic stress. And finally, an angiogenic phenotype, responsible for peribiliary plexus development with sinusoidal arterialization, occurs. In addition, an intense cholangiocyte proliferation, which acquires neuroendocrine abilities, stands out. This histopathological finding is also associated with fibrosis.It is proposed that the sequence of these inflammatory phenotypes, perhaps with a trophic meaning, ultimately produces a benign tumoral biliary process - although it poses severe hepatocytic insufficiency. Moreover, the persistence of this benign tumor disease would induce a higher degree of dedifferentiation and autonomy and, therefore, its malign degeneration.

Hepatic fibrogenesis in response to chronic liver injury: novel insights on the role of cell-to-cell interaction and transition

Hepatic fibrosis represents the wound-healing response process of the liver to chronic injury, independently from aetiology. Advanced liver fibrosis results in cirrhosis that can lead to liver failure, portal hypertension and hepatocellular carcinoma. Currently, no effective therapies are available for hepatic fibrosis. After the definition of hepatic stellate cells (HSCs) as the main liver extracellular matrix-producing cells in the 1980s, the subsequent decade was dedicated to determine the role of specific cytokines and growth factors. Fibrotic progression of chronic liver diseases can be nowadays considered as a dynamic and highly integrated process of cellular response to chronic liver injury. The present review is dedicated to the novel mechanisms of cellular response to chronic liver injury leading to hepatic myofibroblasts' activation. The understanding of the cellular and molecular pathways regulating their function is crucial to counteract therapeutically the organ dysfunction caused by myofibroblasts' activation.

Effects of N-acetylcysteine administration in hepatic microcirculation of rats with biliary cirrhosis

BACKGROUND/AIMS

Increased intrahepatic resistance (IHR) in cirrhosis is due to fibrosis and hepatic endothelial dysfunction (HED). Besides producing fibrosis, increased reactive oxygen species (ROS) promotes ROS-related nitration of anti-oxidative enzymes in cirrhotic livers. Tyrosine nitration (nitrotyrosilation)-related inactivation of anti-oxidative enzymes is increased in cirrhotic livers. This study investigates effects of N-acetylcysteine (NAC) administrations in bile-duct-ligation (BDL) rats.

METHODS

This study measured portal venous pressure (PVP), IHR, hepatic endothelial function, hepatic levels of anti-oxidants and oxidants, type III procollagen (PIIIP), proteins expression of thromboxane synthase (TXS), nitrotyrosine, manganese superoxide dismutase (MnSOD), and hepatic NOx and thromboxane A(2) (TXA(2)) production in perfusates.

RESULTS

The improvement of HED was associated with decreased PVP and IHR, hepatic protein and mRNA levels of PIIIP, protein expression of TXS and nitrotyrosine, oxidants and production of TXA(2) in NAC-treated BDL rat livers. Conversely, hepatic NOx production, anti-oxidants, and protein expression of MnSOD were increased in NAC-treated BDL rat livers.

CONCLUSIONS

In NAC-treated cirrhotic rats, the decrease in IHR was mainly caused by its anti-oxidative effect-related prevention of hepatic fibrogenesis associated with the decrease of oxidants-related nitrotyrosilation and improvement of HED.

Circulating oxidative stress status in desert sheep naturally infected with Fasciola hepatica

Oxidative stress is a general mechanism whereby free radicals induce oxidative damages and reduce the antioxidant defences of the biological systems. The aim of the present study was to determine plasma malondialdehyde levels as a biomarker of lipid peroxidation and its relation to the antioxidants status (plasma ascorbate and blood glutathione concentrations), liver function tests and anaemia in spontaneous ovine fascioliasis. For this purpose, jugular blood samples and livers of 27 infected ewes with Fasciola hepatica along with blood samples of 20 healthy (control) ewes were collected from animals slaughtered in a F. hepatica endemic area (Kharga oasis, Egypt). An increase (P<0.001) in plasma malondialdehyde (141.1%) accompanied by decreased levels (P<0.001) of albumin (29.3%) and ascorbate (36.2%) in plasma and glutathione in blood (31.6%) of infected sheep was noticed when compared with control values. In the infected group, malondialdehyde values were positively correlated with liver fluke burden (r=0.57, P=0.002) and the activity of plasma aspartate aminotransferase (r=0.39, P=0.0.046) and gamma-glutamyltransferase (r=0.64, P=0.0003) and negatively correlated with the concentrations of albumin (r=-0.53, P=0.004), ascorbate (r=-0.46, P=0.0.17) and glutathione (r=-0.41, P=0.034). In conclusion, oxidative stress is a significant feature of chronic F. hepatica infection in grazing sheep.

Pomegranate peel extract prevents liver fibrosis in biliary-obstructed rats

Punica granatum L. (pomegranate) is a widely used plant that has high nutritional value. The aim of this study was to assess the effect of chronic administration of pomegranate peel extract (PPE) on liver fibrosis induced by bile duct ligation (BDL) in rats. PPE (50 mg kg(-1)) or saline was administered orally for 28 days. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels were determined to assess liver function and tissue damage. Proinflammatory cytokines (tumor necrosis factor-alpha and interleukin 1 beta) in the serum and antioxidant capacity (AOC) were measured in plasma samples. Samples of liver tissue were taken for measurement of hepatic malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Production of reactive oxidants was monitored by chemiluminescence assay. Serum AST, ALT, LDH and cytokines were elevated in the BDL group compared with the control group; this increase was significantly decreased by PPE treatment. Plasma AOC and hepatic GSH levels were significantly depressed by BDL but were increased back to control levels in the PPE-treated BDL group. Increases in tissue MDA levels and MPO activity due to BDL were reduced back to control levels by PPE treatment. Similarly, increased hepatic collagen content in the BDL rats was reduced to the level of the control group with PPE treatment. Thus, chronic PPE administration alleviated the BDL-induced oxidative injury of the liver and improved the hepatic structure and function. It therefore seems likely that PPE, with its antioxidant and antifibrotic properties, may be of potential therapeutic value in protecting the liver from fibrosis and oxidative injury due to biliary obstruction.

Endothelium-dependent relaxation of isolated splanchnic arteries from cirrhotic patients: Role of reactive oxygen species

AIM

To examine the endothelium-dependent relaxation of splanchnic arteries during cirrhosis as well as the role of reactive oxygen species in this relaxation using hepatic arteries from cirrhotic patients undergoing liver transplantation and mesenteric arteries from liver donors.

METHODS

Arterial segments 3 mm long were mounted in organ baths for isometric tension recording and precontracted with the thromboxane A(2) analog U46619 (10(-7)-10(-6) M).

RESULTS

The relaxation to acetylcholine (10(-8)-10(-4) M), but not to sodium nitroprusside (10(-8)-10(-4) M) was lower in hepatic arteries. The inhibitor of nitric oxide synthesis, N(omega)-nitro-l-arginine methyl ester (l-NAME, 10(-4) M), the inhibitor of cyclooxygenase, meclofenamate (10(-5) M), or l-NAME (10(-4) M) + meclofenamate (10(-5) M) diminished the relaxation to acetylcholine only in mesenteric arteries. l-NAME (10(-4) M) + meclofenamate (10(-5) M) combined with charybdotoxin (10(-7) M) + apamine (10(-6) M) inhibited the relaxation toacetylcholine in both types of arteries, and this inhibition was greater than with l-NAME + meclofenamate. The scavenger of hydrogen peroxide, catalase (1000 U/mL), the superoxide dismutase mimetic, tiron (10(-2) M) or the inhibitor of NAD(P)H oxidase, diphenyleneiodonium (5 x 10(-6) M), but not the inhibitor of superoxide dismutase, diethyldithiocarbamate (10(-3) M) potentiated the acetylcholine-induced relaxation only in hepatic arteries. l-NAME did inhibit the relaxation to acetylcholine in hepatic arteries pretreated with catalase or tiron.

CONCLUSIONS

Cirrhosis may decrease endothelial release and/or bioavailability of nitric oxide and prostacyclin in splanchnic arteries, which might be caused partly by increased production of reactive oxygen species.

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

BACKGROUND AND AIM

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

METHODS

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

RESULTS

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

DISCUSSION

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

Nuclear factor-E2-related factor 2 expression in liver is critical for induction of NAD(P)H:quinone oxidoreductase 1 during cholestasis

Bile duct ligation (BDL) causes hepatocellular oxidative stress and injury. The transcription factor nuclear factor-E2-related factor (Nrf2) induces expression of numerous genes including NAD(P)H:quinone oxidoreductase 1 (Nqo1) during periods of oxidative stress. Therefore, we hypothesized that BDL increases liver expression of mouse antioxidant genes in an Nrf2-dependent manner. BDL or sham surgeries were performed on male C57BL/6, Nrf2-null, and wild-type mice. Livers were collected at 1, 3, and 7 days after surgery for analysis of messenger ribonucleic acid (mRNA) levels of Nrf2-responsive genes as well as Nqo1 protein and activity. BDL increased mRNA expression of multiple Nrf2 genes in mouse liver, compared to sham-operated controls. Follow-up studies investigating protein expression, enzyme activity, and Nrf2 dependency were limited to Nqo1. Nqo1 protein expression and activity in mouse livers was increased 2- to 3-, and 4- to 5-fold at 3 and 7 days after BDL, respectively. Studies also showed that BDL increases Nqol mRNA, protein expression, and enzyme activity in livers from wild-type mice, but not in Nrf2-null mice. In conclusion, expression of Nrf2-dependent genes is increased during cholestasis. These studies also demonstrate that Nqo1 expression and activity in mouse liver are induced via an Nrf2-dependent mechanism.

Anti-fibrotic effects of tetrandrine on bile-duct ligated rats

Tetrandrine (Tet) (C38H42O8N2; molecular weight, 622), an alkaloid isolated from the Chinese medicinal herb Stephania tetrandra, has been shown to elicit anti-inflammatory and anti-fibrotic effects in pulmonary diseases, but the mechanism of action has yet to be investigated. In this study, we tested whether Tet exerts anti-fibrotic effects on rat hepatic fibrosis through anti-NFkappaB pathways. After bile-duct ligation, rats were given Tet (1 or 5 mg/kg) or silymarin (50 mg/kg, as a positive control) by gavage twice daily for 3 weeks. Liver sections were taken for Sirius red quantitative scoring, immunofluorescence double staining of alpha-smooth muscle actin (alpha-SMA) and NFkappaB, and for quantitative determinations of the mRNA expression levels of TGF-beta1, alpha-SMA, collagen 1alpha2, inducible nitric oxide synthase (iNOS), intercellular adhesion molecule 1 (ICAM-1), metallothionein, vascular endothelial growth factor (VEGF), and VEGF type II receptor (VEGFR2) genes. The results showed that both Tet and silymarin treatment significantly reduced the fibrosis scores and hepatic collagen content of BDL rats, compared with no treatment. Both Tet and silymarin treatments decreased the number of alpha-SMA- and NFkappaB-positive cells in fibrotic livers. Moreover, Tet and silymarin treatments attenuated the mRNA expression levels of TGF-beta1,alpha-SMA, collagen 1alpha2, iNOS, ICAM-1, VEGF, and VEGFR2 genes, and induced the mRNA expression of the metallothionein gene. This study suggests that the anti-fibrotic effects of Tet were related to the reduction of fibrosis-related gene transcription, the attenuation of NFkappaB-activated pathways, and the induction of metallothionein gene transcription in the livers of BDL rats.

Antioxidants vitamin E and C attenuate hepatic fibrosis in biliary-obstructed rats

AIM: To investigate whether antioxidants vitamin E and C can retard development of hepatic fibrosis in the biliary-obstructed rats.

METHODS: Fifty Wistar albino rats were randomly assigned to 5 groups (10 rats in each). Bile duct was ligated in 40 rats and they were treated as follows: group vitC, vitamin C 10 mg/kg sc daily; group vitE, vitamin E 15 mg/kg sc daily; group vitEC, both of the vitamins; bile duct-ligated (BDL, control) group, physiological saline sc. The fifth group was assigned to sham operation. At the end of fourth week, the rats were decapitated, and hepatic tissue biochemical collagen content and collagen surface area were measured. Hepatic tissue specimens were histopathologically evaluated according to Scheuer system. Serum hyaluronate levels were measured by ELISA method.

RESULTS: Despite being higher than sham group, hepatic collagen level was significantly decreased in each of the vitC, vitE and vitEC groups (32.7 ± 1.2, 33.8 ± 2.9, 36.7 ± 0.5 μg collagen/mg protein, respectively) compared to BDL (48.3 ± 0.6 mg collagen/g protein) (P < 0.001 for each vitamin group). Each isolated vitamin C, isolated vitamin E and combined vitamin E/C supplementation prevented the increase in hepatic collagen surface density (7.0% ± 1.1%, 6.2% ± 1.7%, 12.3% ± 2.0%, respectively) compared to BDL (17.4% ± 5.6%) (P < 0.05 for each). The same beneficial effect of vitamin C, vitamin E and combined vitamin E/C treatment was also observed on the decrease of serum hyaluronate levels compared to BDL group (P < 0.001). The relative liver and spleen weights, serum transaminases, cholestatic enzymes, bilirubins and histopathological inflammation scores were not different between the antioxidant treatment groups and the control. However, fibrosis staging scores were obviously reduced only in the vitamin E/C combination group (vit EC: 2.4 ± 0.8 vs BDL: 3.1 ± 0.7; P < 0.05).

CONCLUSION: Each antioxidant vitamin E, vitamin C and their combination retard hepatic fibrosis in biliary-obstructed rats. Oxidative stress may play a role in the pathogenesis of hepatic fibrosis in secondary biliary cirrhosis.

Pathogenesis of primary biliary cirrhosis: A unifying model

Primary biliary cirrhosis (PBC) is a disease of unknown etiology leading to progressive destruction of small intrahepatic bile ducts and eventually to liver cirrhosis and failure. It is characterised by female predominance and serum auto-antibodies to mitochondrial antigens targeting the E2 components of the 2-oxoacid dehydrogenase complex. Although they are associated with disease pathogenesis, no concrete evidence has been presented so far. Epidemiological data indicate that a geographical clustering of cases and possible environmental factors are implicated in pathogenesis. A number of genetic factors play a role in determining disease susceptibility or progression, although no definitive conclusion has been reached so far. A key factor to immune pathogenesis is considered to be the breakdown of immune tolerance, either through molecular mimicry or through the so called determinant density model. In this review, the available data regarding the pathogenesis of primary biliary cirrhosis are described and discussed. A new unifying hypothesis based on early endothelin overproduction in primary biliary cirrhosis (PBC) is presented and discussed.

Anti-TGF-beta strategies for the treatment of chronic liver disease

Permanent alcohol abuse may lead to chronic liver injury with deleterious sequelae such as liver cirrhosis and hepatocellular carcinoma. Mechanisms of fibrogenesis encompass recruitment of inflammatory cells at the site of injury and cytokine mediated activation of hepatic stellate cells (HSC) with accumulation of interstitial collagens. HSC transdifferentiation and accompanying apoptosis result in destruction of liver architecture and are therefore key steps of disease progression. TGF-beta represents the main profibrogenic cytokine in liver fibrosis and other fibroproliferative disorders by inducing extracellular matrix deposition as part of the wound healing response. In parallel, TGF-beta triggers hepatocytes that are strongly responsive for this cytokine, to undergo apoptosis, thereby providing space for HSC proliferation and generation of a collagenous matrix. Anti TGF-beta approaches were established and successfully utilized for the treatment of experimental fibrogenesis. Dominant negative TGF-beta receptors (TbetaR), generated by fusing the Fc domain of human IgG and the N-terminal (extracellular) fragment of TbetaRII (Fc:TbetaRII) were applied to suppress fibrosis. Similarly TGF-beta binding proteins like decorin, antagonistic cytokines such as bone morphogenetic protein-7, hepatocyte growth factor, IL-10, or IFN-gamma were as efficient as camostat mesilate, a protease inhibitor that possibly abrogated proteolytic activation of TGF-beta. Further, our group recently overexpressed Smad7 in bile duct ligation induced liver fibrosis and achieved efficient inhibition of intracellular TGF-beta signaling, thereby counteracting profibrogenic effects in cultured HSC and in vivo. A direct link between the effect of alcohol and TGF-beta exists through reactive oxygen species that are generated in liver cells by alcohol metabolism and represent activators of TGF-beta signaling. Thus, soluble TbetaRII expression reduced experimental fibrogenesis in vitro and in vivo partially by decreasing intracellular ROS and inhibiting NADH oxidase. Approaches that specifically target profibrogenic TGF-beta signaling are promising to treat alcoholic liver disease in the future. However, to ensure safety for the patients to be treated, approaches with strong specificity need to be established. Therefore, it is essential to delineate the profibrogenic actions of TGF-beta and the influence of alcohol abuse in molecular detail.

Antifibrotic effects of Salvia miltiorrhiza on dimethylnitrosamine-intoxicated rats

Excessive oxidative stress is implicated in hepatic fibrogenesis. Extracts of Salvia miltiorrhiza (Sm) have been shown to protect cells against oxidative stress. In this study we investigated the in vitro and in vivo effects of Sm on hepatic fibrosis. A cell line of rat hepatic stellate cells (HSC-T6) was stimulated with transforming growth factor-beta1 (TGF-beta1). The inhibitory effects of Sm (50-400 microg/ml) on TGF-beta1-induced alpha-smooth muscle actin (alpha-SMA) secretion and the mRNA expressions of fibrosis-related genes, including alpha-SMA, connective tissue growth factor (CTGF), and tissue inhibitor of metalloproteinase-1 (TIMP-1), were assessed. Fibrosis was induced by dimethylnitrosamine (DMN) administration in rats. DMN-treated rats were randomly assigned to 1 of 4 groups: saline, Sm (20 mg/kg), Sm (100 mg/kg), or silymarin (100 mg/kg), each given by gavage twice daily for 5 weeks starting from the onset of DMN administration. Sm (200 and 400 microg/ml) significantly inhibited TGF-beta1-stimulated alpha-SMA secretion and the mRNA expressions of alpha-SMA, CTGF, and TIMP-1 in HSC-T6 cells. Fibrosis scores of livers from DMN-treated rats with either a low (1.8 +/- 0.2) or high (1.8 +/- 0.1) dose of Sm, or silymarin (1.4 +/- 0.2) were significantly reduced in comparison with DMN-treated rats receiving saline (3.1 +/- 0.1). Hepatic collagen contents were also significantly reduced by either Sm or silymarin treatment. The mRNA expression levels of alpha-SMA, TGF-beta1, and procollagen I were all attenuated in Sm- and silymarin-treated rats. Moreover, levels of plasma aspartate transaminase activities were reduced by Sm and silymarin treatment. In conclusion, our results show that Sm exerted antifibrotic effects in both HSC-T6 cells and in rats with DMN-induced fibrosis.

Melatonin ameliorates carbon tetrachloride-induced hepatic fibrogenesis in rats via inhibition of oxidative stress

Melatonin is reported to exhibit a wide variety of biological effects, including antioxidant and anti-inflammatory. Evidence shows the important role of oxidative stress in the etiopathogenesis of hepatic fibrosis. The aim of this study was to investigate the protective effects of administration of melatonin in rats with carbon tetrachloride-induced fibrosis for 6 weeks. Hepatic fibrotic changes were evaluated biochemically by measuring tissue hydroxyproline levels and histopathogical examinations. Malondialdehyde (MDA), an end product of lipid peroxidation, and glutathione peroxidase (GSH-px) and superoxide dismutase (SOD) levels were evaluated in tissue homogenates by spectrophotometry. The nuclear factor-kappaB (NF-kappaB) in liver tissue was examined by immunohistochemistry. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) concentrations in Kupffer cells (KCs) culture supernatants were measured with ELISA. The rats injected subcutaneously with CCl4 for 6 weeks resulted in hepatic fibrotic changes increased hydroxyproline and MDA levels, and decreased GSH-px and SOD levels, whereas melatonin reversed these effects. Furthermore, melatonin inhibited the expression of NF-kappaB in liver tissue and decreasing production of proinflammatory cytokines such as TNF-alpha and IL-1beta from KCs in fibrotic rats. These present results suggest that melatonin ameliorates carbon tetrachloride-induced hepatic fibrogenesis in rats via inhibition of oxidative stress and proinflammatory cytokines production.