Nitric oxide-mediated liver injury in the presence of experimental bile duct obstruction

Does lithium attenuate the liver damage due to oxidative stress and liver glycogen depletion in experimental common bile duct obstruction?

In extrahepatic cholestasis, the molecular mechanisms of liver damage due to bile acid accumulation remain elusive. In this study, the activation of glutamatergic receptors was hypothesized to be responsible for bile acid-induced oxidative stress and liver damage. Recent evidence showed that lithium, as an N-methyl-d-aspartate receptor (NMDAR) GluN2B subunit inhibitor, may act on the glutamate/NMDAR signaling axis. Guinea pigs were assigned to four groups, as sham laparotomy (SL), bile duct ligated (BDL), lithium-treated SL (SL + Li) and lithium-treated BDL (BDL + Li) groups. Cholestasis-induced liver injury was evaluated by aspartate aminotransferase (AST), alanine transaminase (ALT), interleukin-6 (IL-6), tissue malondialdehyde (MDA), copper‑zinc superoxide dismutase and reduced glutathione levels. The liability of glutamate/NMDAR signaling axis was clarified by glutamate levels in both plasma and liver samples, with the production of nitric oxide (NO), as well as with the serum calcium concentrations. Blood glucose, glucagon, insulin levels and glucose consumption rates, in addition to tissue glycogen were measured to evaluate the liver glucose-glycogen metabolism. A high liver damage index (AST/ALT) was calculated in BDL animals in comparison to SL group. In the BDL animals, lithium reduced plasma NO and glutamate in addition to tissue glutamate concentrations, while serum calcium increased. The antioxidant capacities and liver glycogen contents significantly increased, whereas blood glucose levels unchanged and tissue MDA levels decreased 3-fold in lithium-treated cholestatic animals. It was concluded that lithium largely protects the cholestatic hepatocyte from bile acid-mediated damage by blocking the NMDAR-GluN2B subunit.

Nesfatin-1 alleviates extrahepatic cholestatic damage of liver in rats

Obstructive jaundice (OJ) can be defined as cessation of bile flow into the small intestine due to benign or malignant changes. Nesfatin-1, recently discovered anorexigenic peptide derived from nucleobindin-2 in hypothalamic nuclei, was shown to have anti-inflammatory and antiapoptotic effects. This study is aimed to investigate the therapeutic effects of nesfatin-1 on OJ in rats. Twenty-four adult male Wistar-Hannover rats were randomly assigned to three groups: sham (n = 8), control (n = 8), and nesfatin (n = 8). After bile duct ligation, the study groups were treated with saline or nesfatin-1, for 10 days. Afterward, blood and liver tissue samples were obtained for biochemical analyses, measurement of cytokines, determination of the oxidative DNA damage, DNA fragmentation, and histopathologic analyses. Alanine aminotransferase and gamma-glutamyl transferase levels were decreased after the nesfatin treatment; however, these drops were statistically non-significant compared to control group (p = 0.345, p = 0.114). Malondialdehyde levels decreased significantly in nesfatin group compared to control group (p = 0.032). Decreases in interleukin-6 and tumor necrosis factor-α levels from the liver tissue samples were not statistically significant in nesfatin group compared to control group. The level of oxidative DNA damage was lower in nesfatin group, however this result was not statistically significant (p = 0.75). DNA fragmentation results of all groups were similar. Histopathological examination revealed that there was less neutrophil infiltration, edema, bile duct proliferation, hepatocyte necrosis, basement membrane damage, and parenchymal necrosis in nesfatin compared to control group. The nesfatin-1 treatment could alleviate cholestatic liver damage caused by OJ due to its anti-inflammatory and antioxidant effects.

The importance of oxidative stress in patients with chronic renal failure whose hypertension is treated with peritoneal dialysis

Increased oxidative stress is a well-known phenomenon in dialysis patients. However, the contribution of hypertension to the oxidative stress in peritoneal dialysis patients has not yet been assessed. The present study aimed to investigate if hypertension had an additional effect on oxidative stress in peritoneal dialysis patients. A total of 50 patients treated with peritoneal dialysis were divided into two groups: The patients with mean of last three blood pressure results as 135/90 mmHg and above were considered hypertensive, the patients with lower blood pressure were considered normotensive. The control group included 25 healthy individuals. Serum malondialdehyde (MDA), advanced oxidation protein product (AOPP), myeloperoxidase (MPO), catalase (CAT) and glutathione peroxidase (GSH-Px) levels were measured in all groups. MDA level, an indicator of lipid peroxidation, was significantly higher in the hypertensive group compared to the control group, while the increase in the normotensive group was not significant. However, the difference between the hypertensive and normotensive groups was significant. The levels of AOPP, an indicator of protein oxidation level, and MPO, an indicator of neutrophil activation, were not different between the groups, while the activities of antioxidant CAT and GSH-Px decreased in both normotensive and hypertensive groups compared to the control group, and there was no significant difference between the patient groups. This study shows that both normotensive and hypertensive peritoneal dialysis patients have increased-oxidative stress and decreased antioxidant levels and hypertension might have an additional effect on oxidative stress by increasing MDA level in peritoneal dialysis patients.

Effects of methylene blue in reducing cholestatic oxidative stress and hepatic damage after bile-duct ligation in rats

The aim of this study was to evaluate the effects of methylene blue against cholestatic oxidative stress and liver damage after ligation of the common bile duct in male Wistar rats. Eight animals were included in each of the following five groups: untreated control, methylene blue control, sham-operated, bile-duct ligation, and bile-duct ligation plus methylene blue. Methylene blue was administered intraperitoneally for 14 days at a daily dose of 2mg/kg per day. All rats were sacrificed 2 weeks following the experimental treatment and the livers of all groups were examined biochemically and histopathologically. The severity of cholestasis and hepatic injury were determined by changes in the plasma, including enzymatic activities: aspartate aminotransferase, alanine aminotransferase, gamma glutamine transferase, and also bilirubin levels. Malondialdehyde, nitric oxide and superoxide dismutase were measured to indicate the oxidative status in the liver tissue. Myeloperoxidase activity and levels of tissue hydroxyproline were determined as measures of neutrophil activation and collagen accumulation, respectively. Liver damage was significantly prevented in the bile-duct ligated rats treated with methylene blue compared with the control bile-duct ligated rats without methylene blue. Treatment with methylene blue markedly reduced activities of serum transaminase, gamma glutamine transferase and bilirubin levels as compared to bile-duct ligated rats without methylene blue. Positive immunolabelling for alpha-smooth muscle actin (alpha-SMA) was increased, especially in vascular smooth muscle cells, fibrotic septa and also around the proliferated bile ducts, after bile-duct ligation. Only weak alpha-SMA immunolabelling was seen in livers of rats treated with methylene blue. These results indicate that methylene blue can attenuate hepatic damage in extrahepatic cholestasis by reducing oxidative stress and inflammatory processes.

Gastric healing effect of melatonin against different gastroinvasive agents in cholestatic rats

BACKGROUND AND OBJECTIVE

The frequency of gastrointestinal ulceration is higher in jaundiced patients than in healthy population. The aim of this study was to assess the effect of pretreatment with melatonin, a potent scavenger of reactive oxygen species, on stress-induced gastric ulcers of cholestatic rats.

MATERIALS AND METHODS

Cholestasis was induced by surgical ligation of bile-duct and sham-operated rats served as sham animals. The animals received saline or melatonin (1, 3 or 10mg/kg) before stress induction. Three different types of gastroinvasive agents including ethanol, indomethacin or water immersion were used as stress agents to induce gastric ulceration.

RESULTS

Gastric mucosal damage induced by different gastroinvasive agents was significantly greater in bile-duct-ligated rats than in sham ones. Melatonin was protective against ethanol-, indomethacin- and water immersion-induced gastric damage in bile-duct-ligated and sham rats, dose-dependently, but the protective effect of melatonin was greater in cholestatic rats than sham rats in all three different series of experiments.

CONCLUSIONS

In conclusion, pretreatment of rats with melatonin protected gastric mucosa of cholestatic rats more effectively than the sham ones possibly by a mechanism involving the scavenging of free radicals.

Reversible surgical model of biliary inflammation and obstructive jaundice in mice

Common bile duct (CBD) ligation is used in animal models to induce biliary inflammation, fibrosis, and cholestatic liver injury, but results in a high early postoperative mortality rate, probably from traumatic pancreatitis. We modified the CBD ligation model in mice by placing a small metal clip across the lower end of the CBD. To reverse biliary obstruction, a suture was incorporated within the clip during its placement. The suture and clip were removed on postoperative d 5 or 10 for biliary decompression. After 5 d of biliary obstruction, the gallbladder showed an 8-fold increase in wall thickness and a 17-fold increase in tissue myeloperoxidase activity. Markedly elevated serum levels of alkaline phosphatase and bilirubin indicated injury to the biliary epithelium and hepatocytes. Early postoperative (d 0-2) survival was 100% and later (d 3-5) survival was 85% (n=54 mice). We successfully reversed biliary obstruction in 20 mice (37%). Overall survival after reversal was 70%. In surviving mice, biliary decompression was complete, inflammation was reduced, and jaundice resolved. Histologic features confirmed reduced epithelial damage, edema, and neutrophil infiltration. Our technique minimized postoperative death, maintained an effective inflammatory response, and was easily reversible without requiring repeat laparotomy. This reversible model can be used to further define molecular mechanisms of biliary inflammation, fibrosis, and liver injury in genetically altered mice.

Protective effect of melatonin on Ca2+ homeostasis and contractility in acute cholecystitis

Impaired Ca2+ homeostasis and smooth muscle contractility co-exist in acute cholecystitis (AC) leading to gallbladder dysfunction. There is no pharmacological treatment for this pathological condition. Our aim was to evaluate the effects of melatonin treatment on Ca2+ signaling pathways and contractility altered by cholecystitis. [Ca2+]i was determined by epifluorescence microscopy in fura-2 loaded isolated gallbladder smooth muscle cells, and isometric tension was recorded from gallbladder muscle strips. Malondialdehyde (MDA) and reduced glutathione (GSH) contents were determined by spectrophotometry and cycloxygenase-2 (COX-2) expression was quantified by western blot. Melatonin was tested in two experimental groups, one of which underwent common bile duct ligation for 2 days and another that was later de-ligated for 2 days. Inflammation-induced impairment of Ca2+ responses to cholecystokinin and caffeine were recovered by melatonin treatment (30 mg/kg). This treatment also ameliorated the detrimental effects of AC on Ca2+ influx through both L-type and capacitative Ca2+ channels, and it was effective in preserving the pharmacological phenotype of these channels. Despite its effects on Ca2+ homeostasis, melatonin did not improve contractility. After de-ligation, Ca2+ influx and contractility were still impaired, but both were recovered by melatonin. These effects of melatonin were associated to a reduction of MDA levels, an increase in GSH content and a decrease in COX-2 expression. These findings indicate that melatonin restores Ca2+ homeostasis during AC and resolves inflammation. In addition, this indoleamine helps in the subsequent recovery of functionality.

REGULATION OF FIBROGENESIS DURING THE EARLY PHASE OF COMMON BILE DUCT OBSTRUCTION

BACKGROUND

Both nitric oxide (NO) and prostaglandins have been proposed as inhibitor substances involved in collagen deposition in the hepatic parenchyma. The possible reciprocal connections between NO and eicosanoids in the development of liver fibrosis were investigated during the initial phase of common bile duct obstructions.

METHODS

A total of 30 male albino guinea pigs were randomly and equally assigned to three groups. Group 1 underwent sham laparotomy. Group 2 and group 3 were subjected to permanent common bile duct ligature for 24 and 72 h, respectively. Changes in the liver prostaglandin E(2) (PGE(2)), leukotriene C(4), malondialdehyde contents and plasma nitrite plus nitrate concentrations were measured. To evaluate the extent of hepatic fibrosis, histological assessment of liver was confirmed with the equivalent hydroxyproline contents of liver.

RESULTS

Twenty-four hours after ligature, the amount of malondialdehyde and PGE(2) and plasma nitrite plus nitrate concentrations increased significantly, whereas liver hydroxyproline contents did not change. However, 72 h after ligature (Group 3), lipid peroxidation and collagen deposition were significantly higher than that of the group 2 animals. The PGE(2) : leukotriene C(4) ratio peaked at 24 h and later decreased, whereas PGE(2) : NO ratio remained unchanged in both group 2 and group 3 animals.

CONCLUSIONS

The initiation of collagen synthesis occurred in portal tract as early as within the first 72 h of bile duct obstruction. The optimum function of reactive oxygen species on the stellate cell activation might be determined by the interaction between NO and PGE(2).

Successively postadministered melatonin prevents disruption of hepatic antioxidant status in rats with bile duct ligation

We have reported that orally administered melatonin exerts a therapeutic effect on cholestatic liver injury in rats treated with bile duct ligation (BDL) possibly through its antioxidant and anti-inflammatory actions. Herein, we examined whether successively postadministered melatonin prevents the disruption of hepatic antioxidant status in BDL-treated rats. Wistar rats with BDL were killed 5 and 13 days after BDL. Melatonin (10 or 100 mg/kg body weight) was orally administered to rats with and without BDL everyday for 8 days, starting 5 days after BDL. The hepatic concentrations of thiobarbituric acid reactive substances, an index of lipid peroxidation, and reduced glutathione increased 5 days after BDL and further increased at 13 days. Hepatic vitamin E concentration and catalase and Se-glutathione peroxidase (Se-GSH-Px) activities were similarly reduced at 5 and 13 days after BDL. Hepatic ascorbic acid concentration and the hepatic activities of Cu,Zn- and Mn-superoxide dismutases, glutathione reductase, and glucose-6-phosphate dehydrogenase decreased 13 days after BDL. Melatonin postadministered to BDL-treated rats attenuated all these changes observed at 13 days after the treatment more effectively at the higher dose than at the lower dose. Melatonin administered to BDL-untreated rats increased the hepatic Se-GSH-Px activity at both doses and the hepatic activities of Cu,Zn- and Mn-superoxide dismutases at the higher dose. These results indicate that successively postadministered melatonin at pharmacological doses prevents the disruption of hepatic antioxidant status in rats with BDL through its direct and indirect antioxidant action, which may contribute to its therapeutic effect of BDL-induced cholestatic liver injury.

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.

Protective effect of low dose of melatonin against cholestatic oxidative stress after common bile duct ligation in rats

AIM: To investigate the role of oxidative injury and the effect of exogenous melatonin administration on liver damage induced by bile duct ligation (BDL), and second, to evaluate the role of nitric oxide (NO), a free oxygen radical, in oxidative injury.

METHODS: Thirty-two Sprague-Dawley rats were assigned to four groups: sham operation (SO), BDL, BDL+melatonin, and BDL+vehicle. Cholestasis was achieved by double ligature of the common bile duct. Melatonin was injected intraperitoneally 500 µg/(kg·d) for 8 d. Hepatic oxidative stress markers were evaluated by changes in the amount of lipid peroxides, measured as malondialdehyde (MDA), and reduced GSH. Total nitrite (NO_X) concentrations were determined in hepatic homogenates. Histopathological examination was performed using a histological scoring system.

RESULTS: The histopathological changes including portal inflammation, necrosis, apoptosis, focal inflammation and fibrosis were severe in the BDL and BDL+vehicle groups. There were numerous large areas of coagulation necrosis. Histological Activity Index scores of these groups were significantly higher than that of the SO group. Treatment with melatonin reduced these alterations significantly. The degree of necro-inflammation and fibrosis showed significant difference between the BDL and BDL+melatonin groups. BDL was accompanied by a significant increase in MDA and NO_X, and a significant decrease in GSH levels. Mean±SE values of MDA, GSH and NO_X levels of SO group were 147.47±6.69, 0.88±0.33 µmol/g and 180.70±6.58 nm/g, respectively. The values of BDL group were 200.14±21.30, 0.65±0.02 µmol/g, and 400.46±48.89 nm/g, respectively, whereas the values of BDL+melatonin group were 115.93±6.8, 0.74±0.02 µmol/g, and 290.38±32.32 nm/g, respectively. Melatonin treatment was associated with a significant recovery of MDA, GSH and NO_X levels.

CONCLUSION: We have concluded that oxidative stress is associated with the pathogenesis of cholestatic liver damage and NO contributes to oxidative damage. Melatonin, even at low dose, is an efficient agent in reducing negative parameters of cholestasis.

FR167653 attenuates murine immunological liver injury

AIM: To study the effect of FR167653 on immunological liver injury (ILI) in mice.

METHODS: ILI was established by tail vein injection of 2.5 mg Bacillus Calmette-Guerin (BCG), and 10 d later with 10 mg lipopolysaccharide (LPS) in 0.2 mL saline (BCG plus LPS). Alanine aminotransferase (ALT), aspartate aminotransferase (AST) in sera and malondialdehyde (MDA), glutathione peroxidase (GSHpx) contents in liver homogenates were assayed by spectrophotometry. The levels of tumor necrosis factor-α (TNF-α ) and nitric oxide (NO) levels in sera were determined using ELISA. Interleukin-1 (IL- 1) produced by peritoneal macrophages was determined by the method of ³ H- infiltrated cell proliferation. The nuclear factor-kappa B (NF-κ B) p65 in liver tissue was analyzed with reverse transcription polymerase chain reaction (RT-PCR) . Liver samples collected were stained with hematoxylin and eosin.

RESULTS: FR167653 (50, 100, 150 mg/kg) could significantly decrease the serum transaminase (ALT, AST) activity and MDA content in liver homogenate, and improve reduced GSHpx level of liver homogenate. Liver histopathological examination showed FR167653 (100, 150 mg/kg) significantly reduced inflammatory cells infiltration and liver cells necrosis. FR167653 (50, 100, 150 mg/kg) significantly lowered TNF- α and NO levels in serum, and IL-1 produced by peritoneal macrophages. Moreover, expression of NF-κ B mRNA in liver tissue of ILI induced by BCG plus LPS was significantly reduced by FR167653.

CONCLUSION: All results showed that FR167653 had significant inhibitory action on ILI in mice.