Brain Oxidative Stress Induced by Obstructive Jaundice in Rats

Evaluation of oxidative damage to biomolecules and inflammation in patients with urea cycle disorders

Urea cycle disorders (UCD) are inborn errors of metabolism that occur due to a loss of function in enzymes and transporters involved in the urea cycle, causing an intoxication by hyperammonemia and accumulation of metabolites. Patients can develop hepatic encephalopathy (HE), severe neurological and motor disabilities, and often death. The mechanisms involved in the pathophysiology of UCD are many and complex, but there are strong indications that oxidative stress and inflammation are present, being responsible for at least part of the cellular damage that occurs in these diseases. The aim of this study was to evaluate oxidative and nitrosative damage and inflammation in UCD, to better understand the pathophysiology mechanisms of these diseases. We evaluated the nitrite and nitrate content, thiobarbituric acid-reactive substances (TBARS), carbonyl protein content and a panel of cytokines in plasma sample of 14 patients. The UCD patients group consisted of individuals affected with ornithine transcarbamylase deficiency (n = 8), carbamoyl phosphate synthetase deficiency (n = 2), argininosuccinate synthetase deficiency (n = 2); arginase 1 deficiency (n = 1) and argininosuccinate lyase deficiency (n = 1). Patients mean age at diagnosis was 5.25 ± 9.86 years-old and mean concentrations were compared with healthy individuals of matched age and gender. We found a significant reduction in nitrogen reactive species in patients when compared to controls. TBARS was increased in patients, indicating lipid peroxidation. To evaluate protein oxidative damage in UCD, the carbonyl content was measured, and the results also demonstrated an increase in this biomarker. Finally, we found that UCD patients have enhanced concentrations of cytokines, with pro-inflammatory interleukins IL-6, IL-8, interferon-γ and TNF-α, and anti-inflammatory IL-10 being increased when compared to the control group. In conclusion, our results demonstrate that oxidative stress and inflammation occurs in UCD and probably contribute to the severe brain damage present in patients.

Time progression and regional expression of brain oxidative stress induced by obstructive jaundice in rats

BACKGROUND

Obstructive jaundice induces oxidative changes in the brain parenchyma and plays significant role in clinical manifestations of hepatic encephalopathy. We aim to study the progression of the brain oxidative status over time and the differences of its pattern over the hemispheres, the brainstem and the cerebellum. We use an experimental model in rats and measuring the oxidative stress (OS) specific biomarkers protein malondialdehyde (PrMDA) and protein carbonyls (PrC = O).

RESULTS

Hyperbilirubinemia has been confirmed in all study groups as the result of common bile duct obstruction. We confirmed increase in both PrMDA and PrC = O biomarkers levels with different type of changes over time. We also confirmed that the oxidative process develops differently in each of the brain areas in study.

CONCLUSIONS

The present study confirms the progressive increase in OS in all brain areas studied using markers indicative of cumulative protein modification.

Overview of oxidative stress findings in hepatic encephalopathy: From cellular and ammonium-based animal models to human data

Oxidative stress is a natural phenomenon in the body. Under physiological conditions intracellular reactive oxygen species (ROS) are normal components of signal transduction cascades, and their levels are maintained by a complex antioxidants systems participating in the in-vivo redox homeostasis. Increased oxidative stress is present in several chronic diseases and interferes with phagocytic and nervous cell functions, causing an up-regulation of cytokines and inflammation. Hepatic encephalopathy (HE) occurs in both acute liver failure (ALF) and chronic liver disease. Increased blood and brain ammonium has been considered as an important factor in pathogenesis of HE and has been associated with inflammation, neurotoxicity, and oxidative stress. The relationship between ROS and the pathophysiology of HE is still poorly understood. Therefore, sensing ROS production for a better understanding of the relationship between oxidative stress and functional outcome in HE pathophysiology is critical for determining the disease mechanisms, as well as to improve the management of patients. This review is emphasizing the important role of oxidative stress in HE development and documents the changes occurring as a consequence of oxidative stress augmentation based on cellular and ammonium-based animal models to human data.

Central nervous system and systemic oxidative stress interplay with inflammation in a bile duct ligation rat model of type C hepatic encephalopathy

The role and coexistence of oxidative stress (OS) and inflammation in type C hepatic encephalopathy (C HE) is a subject of intense debate. Under normal conditions the physiological levels of intracellular reactive oxygen species are controlled by the counteracting antioxidant response to maintain redox homeostasis. Our previous in-vivo¹H-MRS studies revealed the longitudinal impairment of the antioxidant system (ascorbate) in a bile-duct ligation (BDL) rat model of type C HE. Therefore, the aim of this work was to examine the course of central nervous system (CNS) OS and systemic OS, as well as to check for their co-existence with inflammation in the BDL rat model of type C HE. To this end, we implemented a multidisciplinary approach, including ex-vivo and in-vitro electron paramagnetic resonance spectroscopy (EPR) spin-trapping, which was combined with UV-Vis spectroscopy, and histological assessments. We hypothesized that OS and inflammation act synergistically in the pathophysiology of type C HE. Our findings point to an increased CNS- and systemic-OS and inflammation over the course of type C HE progression. In particular, an increase in the CNS OS was observed as early as 2-weeks post-BDL, while the systemic OS became significant at week 6 post-BDL. The CNS EPR measurements were further validated by a substantial accumulation of 8-Oxo-2'-deoxyguanosine (Oxo-8-dG), a marker of oxidative DNA/RNA modifications on immunohistochemistry (IHC). Using IHC, we also detected increased synthesis of antioxidants, glutathione peroxidase 1 (GPX-1) and superoxide dismutases (i.e.Cu/ZnSOD (SOD1) and MnSOD (SOD2)), along with proinflammatory cytokine interleukin-6 (IL-6) in the brains of BDL rats. The presence of systemic inflammation was observed already at 2-weeks post-surgery. Thus, these results suggest that CNS OS is an early event in type C HE rat model, which seems to precede systemic OS. Finally, our results suggest that the increase in CNS OS is due to enhanced formation of intra- and extra-cellular ROS rather than due to reduced antioxidant capacity, and that OS in parallel with inflammation plays a significant role in type C HE.

The neurogliovascular unit in hepatic encephalopathy

Hepatic encephalopathy (HE) is a neurological complication of hepatic dysfunction and portosystemic shunting. It is highly prevalent in patients with cirrhosis and is associated with poor outcomes. New insights into the role of peripheral origins in HE have led to the development of innovative treatment strategies like faecal microbiota transplantation. However, this broadening of view has not been applied fully to perturbations in the central nervous system. The old paradigm that HE is the clinical manifestation of ammonia-induced astrocyte dysfunction and its secondary neuronal consequences requires updating. In this review, we will use the holistic concept of the neurogliovascular unit to describe central nervous system disturbances in HE, an approach that has proven instrumental in other neurological disorders. We will describe HE as a global dysfunction of the neurogliovascular unit, where blood flow and nutrient supply to the brain, as well as the function of the blood-brain barrier, are impaired. This leads to an accumulation of neurotoxic substances, chief among them ammonia and inflammatory mediators, causing dysfunction of astrocytes and microglia. Finally, glymphatic dysfunction impairs the clearance of these neurotoxins, further aggravating their effect on the brain. Taking a broader view of central nervous system alterations in liver disease could serve as the basis for further research into the specific brain pathophysiology of HE, as well as the development of therapeutic strategies specifically aimed at counteracting the often irreversible central nervous system damage seen in these patients.

Investigation of possible neuroprotective effects of some plant extracts on brain in bile duct ligated rats

This study aimed to investigate the possible neuroprotective effects of bitter melon (BM), chard, and parsley extracts on oxidative damage that may occur in the brain of rats with bile duct ligation (BDL)-induced biliary cirrhosis. It was observed that lipid peroxidation (LPO), sialic acid (SA), and nitric oxide (NO) levels increased; glutathione (GSH) levels, catalase (CAT) activity, and tissue factor (TF) activity decreased significantly in the BDL group. However, in groups with BDL given BM, chard, and parsley extracts LPO, SA, NO levels decreased; GSH levels and CAT activities increased significantly. No significant differences were observed between groups in total protein, glutathione-S-transferase, superoxide dismutase, and boron. Histological findings were supported by the biochemical results. BM, chard, and parsley extracts were effective in the regression of oxidant damage caused by cirrhosis in the brain tissues. PRACTICAL APPLICATIONS: Bitter melon (BM), chard, and parsley have antioxidant properties due to their bioactive compounds which are involved in scavenging free radicals, suppressing their production, and stimulating the production of endogenous antioxidant compounds. Since BM, chard, and parsley extracts were found to be effective in the regression of oxidant damage caused by cirrhosis in the brain tissues, these plant extracts may be an alternative in the development of different treatment approaches against brain damage in cirrhosis. At the same time, these species have been used as food by the people for many years. Therefore, they can be used safely as neuroprotective agents in treatment.

Effect of cholestasis and NeuroAid treatment on the expression of Bax, Bcl-2, Pgc-1α and Tfam genes involved in apoptosis and mitochondrial biogenesis in the striatum of male rats

Cholestasis means impaired bile synthesis or secretion. In fact, it is a bile flow reduction following Bile Duct Ligation (BDL). Cholestasis has a main role in necrosis and apoptosis. Apoptosis is a form of programmed cell death that has intrinsic and extrinsic pathways. The intrinsic pathway is mediated by Bcl-2 (B cell lymphoma-2) proteins which integrate death and survival signals. Bcl-2 has anti-apoptotic and Bax has pro-apoptotic effects. Also, striatum is one of the brain regions that has high expressions of Bcl-2 proteins. Moreover, Tfam and Pgc-1α are involved in mitochondrial biogenesis. On the other hand, NeuroAid, is a drug that has neuroprotective and anti-apoptosis effects. In this study, using quantitative PCR, we measured the expression of all these genes in the striatum of male rats following BDL and NeuroAid administration. Results showed, BDL increased the expression of Bax and Tfam and decreased the expression of Bcl-2. NeuroAid restored the effect of BDL on the expression of Bax, while did not alter the effect of BDL on Bcl-2. In addition, it increased the expression of Tfam that was previously elevated by BDL and raised the expression of Tfam in normal rats. Both BDL and NeuroAid, had no effect on Pgc-1α. In conclusion, cholestasis increased the expression of Bax and decreased the expression of Bcl-2, and this effect may have related to enhanced susceptibility of mitochondrial pathways following oxidative stress. Tfam expression was increased following cholestasis and this effect may have related to cellular compensatory mechanisms against high accumulation of free radicals or mitochondrial biogenesis failure. Furthermore, NeuroAid may play a role against apoptosis and can be used to increase mitochondrial biogenesis.

Mitochondrial dysfunctions contribute to energy deficits in rodent model of hepatic encephalopathy

Perturbations in the cerebral energy metabolism are anticipated to be an important factor by which ammonia may exert its toxic effects on the central nervous system. The present study was designed to investigate the role of impaired mitochondrial functions and cerebral energy metabolism in the development hepatic encephalopathy (HE) induced by of bile duct ligation (BDL). After four weeks of BDL, a significant increase in hepatic hydroxyproline and collagen content was observed which confirmed biliary fibrosis. Brain regions viz. cortex, hippocampus, striatum and cerebellum of BDL rats had impaired activity of mitochondrial respiratory chain enzymes. This was accompanied by increase in mitochondrial reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl levels in the brain. Mitochondrial redox ratio was significantly reduced in the brain of BDL rats. In addition, mitochondria from brain of BDL rats were depolarized and swollen compared to the sham controls. Ultrastructure analysis of mitochondria from cortex and hippocampus of BDL animals revealed aberrant cristae, ruptured membranes and non-dense matrix. Further, a significant decrease was observed in creatine kinase activity, glucose uptake and CO₂ production in the brain regions of BDL rats. ATP/ADP ratio, a critical parameter of cellular energy status, was also significantly reduced in brain regions of rats with HE. Overall, the findings clearly demonstrate that BDL induced HE involves mitochondrial respiratory chain dysfunctions, mitochondrial depolarization and swelling that accentuates oxidative stress which in turn leads to compromise in cerebral energy metabolism thereby contributing to the pathophysiology of chronic HE.

Ginsenoside Rg1 prevents cerebral and cerebellar injury induced by obstructive jaundice in rats via inducing expression of TIPE-2

The aim of the study was to analyze the effect of Ginsenoside Rg1 (Rg1) on cerebral and cerebellar injury in experimental obstructive jaundice (OJ). OJ was done by ligature and section of extrahepatic biliary duct. Rg1 was injected intraperitoneally (10 mg kg(-1)d(-1) or 20 mg kg(-1) d(-1)). Comparison of serum total bile salts (TBA), total bilirubin (TBil), direct bilirubin (DBil), TNF-α, IL-6 and IL-1β among groups. Malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were determined, also apoptosis and mRNA and protein levels of TIPE2 (TNF-α-inducible protein 8-like 2) were tested in cerebrum and cerebellum. Our results showed that Rg1 reduced MDA and apoptosis in cerebrum and cerebellum induced by OJ, also GSH and antioxidant enzyme activity were raised obviously in rats treated with Rg1. Moreover, decreased mRNA and protein levels of TIPE2 in OJ rats and Rg1 could improve the decreased mRNA and protein levels of TIPE2 in OJ rats. In conclusion, Rg1 decreased oxidative stress and apoptosis, also recovered the antioxidant status and mRNA and protein levels of TIPE2 in the cerebrum and cerebellum of OJ rats.

Metabolomics changes in a rat model of obstructive jaundice: mapping to metabolism of amino acids, carbohydrates and lipids as well as oxidative stress

The study examined the global metabolic and some biochemical changes in rats with cholestasis induced by bile duct ligation (BDL). Serum samples were collected in male Wistar rats with BDL (n = 8) and sham surgery (n = 8) at day 3 after surgery for metabolomics analysis using a combination of reversed phase chromatography and hydrophilic interaction chromatography (HILIC) and quadrupole-time-of-flight mass spectrometry (Q-TOF MS). The serum levels of malondialdehyde (MDA), total antioxidative capacity (T-AOC), glutathione (GSH) and glutathione disulfide (GSSG), the activities of superoxide dismutase (SOD) and glutathion peroxidase (GSH-Px) were measured to estimate the oxidative stress state. Key changes after BDL included increased levels of l-phenylalanine, l-glutamate, l-tyrosine, kynurenine, l-lactic acid, LysoPC^c (14:0), glycine and succinic acid and decreased levels of l-valine, PC^b (19:0/0:0), taurine, palmitic acid, l-isoleucine and citric acid metabolism products. And treatment with BDL significantly decreased the levels of GSH, T-AOC as well as SOD, GSH-Px activities, and upregulated MDA levels. The changes could be mapped to metabolism of amino acids and lipids, Krebs cycle and glycolysis, as well as increased oxidative stress and decreased antioxidant capability. Our study indicated that BDL induces major changes in the metabolism of all 3 major energy substances, as well as oxidative stress.

Occludin dislocation in brain capillary endothelium of rats with bile duct ligation induced cholestasis

The present study used a rat model with bile duct ligation to examine the effect of cholestasis, to the localization of occludin in brain capillary endothelium by means of electronic microscopy. The results demonstrated a dislocation of occludin away from the tight junction sites of brain endothelial cells. A significant increase of the occludin-interendothelial cleft distance was demonstrated in the midbrain and the cerebellum samples but not in the frontal cortex, compared to the control group samples. These findings imply a brain region selective derangement of occludin in response to liver disease.

Melatonin protects against taurolithocholic-induced oxidative stress in rat liver

Cholestasis, encountered in a variety of clinical disorders, is characterized by intracellular accumulation of toxic bile acids in the liver. Furthermore, oxidative stress plays an important role in the pathogenesis of bile acids. Taurolithocholic acid (TLC) was revealed in previous studies as the most pro-oxidative bile acid. Melatonin, a well-known antioxidant, is a safe and widely used therapeutic agent. Herein, we investigated the hepatoprotective role of melatonin on lipid and protein oxidation induced by TLC alone and in combination with FeCl(3) and ascorbic acid in rat liver homogenates and hepatic membranes. The lipid peroxidation products, malondialdehyde and 4-hydroxyalkenals (MDA + 4-HDA), and carbonyl levels were quantified as indices of oxidative damage to hepatic lipids and proteins, respectively. In the current study, the rise in MDA + 4-HDA levels induced by TLC was inhibited by melatonin in a concentration-dependent manner in both liver homogenates and in hepatic membranes. Melatonin also had protective effects against structural damage to proteins induced by TLC in membranes. These results suggest that the indoleamine melatonin may potentially act as a protective agent in the therapy of those diseases that involve bile acid toxicity.

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.

Cholestasis induces apoptosis in mice cardiac cells: the possible role of nitric oxide and oxidative stress

BACKGROUND/AIMS

Acute cholestasis is associated with cardiovascular complications. The purpose of the present study was to investigate the effect of cholestasis on heart apoptosis and the involvement of nitric oxide (NO) and oxidative stress in the possible altered apoptosis of cholestatic hearts.

METHODS

Cholestasis was induced by bile duct-ligation, and sham-operated mice served as controls. Three days after the surgery, heart tissues were evaluated for apoptosis and the level of malondialdehyde (MDA), and the activities of catalase (CAT), glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) have been studied in cardiac tissues. The role of treatment with l-NAME, a non-selective inhibitor of NO synthase, or with d-NAME, an inactive isomer of l-NAME, on cholestatic and sham cardiac apoptosis, level of MDA and CAT, SOD and GSHPx activities was also investigated. The content of NO in cardiac tissue was also determined.

RESULTS

Cholestatic hearts showed structural abnormalities and increased apoptosis compared with sham hearts. Treatment with l-NAME, but not d-NAME, improved both structural abnormalities and enhanced apoptosis of cholestatic hearts. Cholestatic hearts also had an increased level of MDA and decreased activities of CAT and GSHPx, which were not modified by d-NAME treatment. By l-NAME treatment, the level of MDA decreased and activities of CAT, GSHPx and SOD increased in BDL mice. The content of NO was higher in cholestatic cardiac tissue, which was decreased by l-NAME treatment.

CONCLUSION

In conclusion, apoptosis in cholestatic heart might have occurred because of NO overproduction, which could induce oxidative stress in the heart of cholestatic mice.

Altered occludin expression in brain capillaries induced by obstructive jaundice in rats

The development of increased oxidative stress in the context of obstructive cholestasis has been proven in various rats' organs including the brain. The present study aimed to detect alterations of tight junction-associated occludin in rat brain capillaries after bile duct ligation (BDL). In experiment 1, occludin expression was evaluated by Western blot analysis in 5 animals 10 days after BDL and compared with 5 sham-operated ones. In experiment 2, groups of 9 animals each were used to assess occludin levels on the 1st, 5th, and 10th days after BDL and to associate these measurements with the in vivo superoxide radical production measured by means of an ultrasensitive fluorescent assay. The results indicated that occludin expression in BDL animals, as opposed to sham-operated, was significantly reduced at every time point studied, being lowest in the rats remaining on BDL condition for 10 days. Moreover, it was demonstrated that the time-dependent downregulation of occludin expression in the brain endothelial was significantly correlated with the time-dependent increase of brain superoxide radical level, implying a relationship between these two abnormalities. In conclusion, the evidence presented herein suggests the implication of occludin and, therefore, of blood-brain barrier in the pathophysiology of extrahepatic cholestasis.

Time-related alterations of superoxide radical levels in diverse organs of bile duct-ligated rats

The time-related alterations of superoxide radical measured in vivo by employing an ultrasensitive fluorescent assay in the liver, intestine, kidney and brain of rats with experimentally induced obstructive jaundice was investigated. Eighteen rats were randomly divided into Group A, rats subjected to sham operation, and Group B, rats subjected to bile duct ligation (BDL). Three rats from each group were subsequently killed at different time points post-operatively (1, 5 and 10 days). As compared to sham-operated, BDL rats showed a gradual increase with time of superoxide radical in the intestine, liver, kidney and brain: for animals sacrificed on the 1(st), 5(th) and 10(th) day the increase was 45%, 50% and 96% in the liver, 76%, 81% and 118% in the intestine, 64%, 71% and 110% in the kidney and 76%, 95% and 142% in the brain, respectively. This study provides direct evidence of an early appearance of oxidative stress in diverse organs, implying a uniform systemic response to biliary obstruction and emphasizing the need of early bile flow restoration.

Metabolism of polyamines and oxidative stress in the brain of cholestatic rats

In a recently published article in "Amino Acids" it was shown that obstructive jaundice of 9 days' duration in rats induces significant alterations of polyamines' metabolism in the brain, which might play an important pathogenetic role in cholestatic brain injury. The authors proposed that alterations of polyamines in cholestatic brain might induce neuronal toxicity through a mechanism that implicates the production of reactive oxygen species and oxidative stress, although this parameter was not evaluated in their study. This hypothesis is supported by our recent findings on brain oxidative status in rats with obstructive jaundice of 10 days' duration. Potential interrelations of the two studies' findings are discussed in this commentary.

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.

Superoxide radical formation in diverse organs of rats with experimentally induced obstructive jaundice

Oxidative stress seems to be a cardinal feature of cholestasis, implicated in the pathophysiology of organ injury not only in the liver, but also in several extrahepatic tissues. The present study was designed to assess directly oxidative stress in vital organs of experimentally jaundiced rats by measuring the key oxidative stress marker superoxide radical (O2(*-)). Twelve male Wistar rats underwent laparotomy and were divided into two groups - group I (n = 6) sham operated, and group II (n = 6) bile-duct ligated. Ten days later, the O2(*-) formation rate was quantified in liver, intestine, kidney and heart of all animals. These measurements were done by application of a new ultrasensitive fluorescent assay for the in vivo quantification of O2(*-), which is based on the 1:1 molar stoichiometric reaction of O2(*-) with dihydroethidine (DHE, an O2(*-) trap) that results in the formation of the specific product 2-OH-ethidium. 2-OH-Ethidium was measured by fluorescence in rats' organs and its formation rate was converted to O2(*-) production rate. As compared to sham-operated rats, in jaundiced rats there was a significant increase of O2(*-) in the intestine (136%, P < 0.01), liver (104%, P < 0.01), and kidney (95%, P < 0.01), whereas there was no significant difference in heart O2(*-) levels. Superoxide radical may play an important role in the pathophysiology of cholestatic liver injury, intestinal barrier failure and renal failure, associated with postoperative morbidity and mortality in obstructive jaundice. On the contrary, O2(*-) and oxidative stress are possibly not implicated in the pathophysiology of hepatic cardiomyopathy.

Melatonin prevents brain oxidative stress induced by obstructive jaundice in rats

The aim of the study was to analyze the impact of melatonin on brain oxidative stress in experimental biliary obstruction. Cholestasis was done by a double ligature and section of the extrahepatic biliary duct. Melatonin was injected intraperitoneally (500 microg/kg/day). Malondialdehyde (MDA), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) contents were determined in the brain tissue. Biliary obstruction raised MDA and reduced GSH contents in the cortex, cerebellum, and hypothalamus areas. Moreover, the scavenger enzyme activity significantly dropped in all areas of the brain. Melatonin drastically reduced MDA concentration and enhanced GSH concentration, as well as all antioxidant enzyme activity in all brain areas obtained from the bile duct-ligated animals. In conclusion, the treatment with melatonin decreased lipid peroxidation and recovered the antioxidant status in the brain from cholestatic animals.

Unconjugated bilirubin differentially affects the redox status of neuronal and astroglial cells

We investigated whether nerve cell damage by unconjugated bilirubin (UCB) is mediated by oxidative stress and ascertained the neuronal and astroglial susceptibility to injury. Several oxidative stress biomarkers and cell death were determined following incubation of neurons and astrocytes isolated from rat cortical cerebrum with UCB (0.01-1.0 microM). We show that UCB induces a dose-dependent increase in neuronal death in parallel with the oxidation of cell components and a decrease in the intracellular glutathione content. Comparison of the results obtained in both cell types demonstrates that neurons are more vulnerable than astrocytes to oxidative injury by UCB, for which accounts the lower glutathione stores in neuronal cells. Moreover, neuronal oxidative injury is prevented by supplementation with N-acetylcysteine, a glutathione precursor, whereas astroglial sensitivity to UCB is enhanced by inhibition of glutathione synthesis, using buthionine sulfoximine. Collectively, we demonstrate that oxidative stress is involved in UCB neurotoxicity and depict a new therapeutic approach for UCB-induced oxidative damage.

Effect of N-acetylcysteine, allopurinol and vitamin E on jaundice-induced brain oxidative stress in rats

We examined the possible protective effect of certain antioxidants (N-acetylcysteine, allopurinol and vitamin E) against the oxidative stress of brain tissue induced by experimental obstructive jaundice in rats. Thirty-six male Wistar rats were randomly divided into six groups; group I control, group II sham operated, group III bile duct ligated and groups IV, V, and VI in which the rats, after bile duct ligation, were given every day an intraperitoneal injection with N-acetylcysteine, allopurinol and Vit-E respectively. All rats were sacrificed on the tenth day by exsanguination and the oxidative state in samples from cortex, midbrain and cerebellum was assessed by measuring the thiol redox state and lipid peroxidation quantified by MDA measurements. The main finding was that all three antioxidants decrease lipid peroxidation in the three brain areas. Cysteine levels increased and protein thiol levels were reserved only in the group treated with N-acetylcysteine, whereas oxidized glutathione increased dramatically in the group treated with allopurinol, suggesting that each antioxidant agent had a certain influence profile on the different antioxidant defense systems. The observed effects of the antioxidants in this experimental model could also provide insight into some aspects of jaundice-induced hepatic encephalopathy in humans.