Oxidant injury to hepatic mitochondria in patients with Wilson's disease and Bedlington terriers with copper toxicosis

Effect of chronic exposure to excess dietary copper and dietary selenium supplementation on liver specimens from rats

OBJECTIVE

To determine the effects of chronic exposure to excess dietary copper (Cu) on liver specimens from rats and the effects of dietary selenium (Se) supplementation in experimental Cu toxicosis.

ANIMALS

60 weanling male Fischer 344 rats.

PROCEDURE

Rats were randomly assigned to 4 groups of 15 rats each and fed 1 of the following 4 diets: high Cu (500 microg/g)/adequate Se (0.2 microg/g); high Cu (500 microg/g)/supplemented Se (2 microg/g); adequate Cu (18 microg/g)/adequate Se (0.2 microg/g); or, adequate Cu (18 microg/g)/supplemented Se (2 microg/g). Five rats per group were euthanatized after 3, 6, and 12 months, and liver specimens were obtained for histologic examination, histochemistry, metal analysis by atomic absorption spectrophotometry, measurement of glutathione peroxidase activity, and assessment of lipid peroxidation, using quantification of malondialdehyde (MDA) by the thiobarbituric acid reaction.

RESULTS

Hepatic Cu concentration was significantly higher in rats fed high Cu diets (range, 9 to 18 microg/g of tissue [wet weight]), compared with rats receiving adequate Cu diets (4.0 to 5.7 microg/g of tissue). Rats fed high-Cu diets for 3, 6, and 12 months had mild multifocal hepatitis often surrounding necrotic foci. However, an increase in hepatic MDA content, indicative of lipid peroxidation, was not detected in these rats. Development of morphologic changes was not prevented by use of dietary Se supplementation.

CONCLUSION AND CLINICAL RELEVANCE

Long-term exposure to excess dietary Cu caused mild hepatic lesions in Fischer 344 rats. Dietary Se supplementation did not prevent hepatic damage in rats with Cu toxicosis.

Tumor suppressor protein p53 mRNA and subcellular localization are altered by changes in cellular copper in human Hep G2 cells

Copper toxicity causes hepatic damage that can lead to the development of hepatocarcinoma. Similarly, copper deficiency has been reported to increase hepatocyte tumorigenesis. Thus, the objective of this work was to explore the role of copper toxicity and deficiency in the regulation of the tumor suppressor protein p53. Using Northern analysis, Western analysis, immunocytochemistry and the human hepatoma cell line Hep G2, this work showed that elevations in hepatocyte copper consistent with Wilson's disease (5.7-fold increase) induced p53 mRNA and confirmed that copper toxicity is correlated with apoptotic cell death. However, Western analysis and immunocytochemistry showed that post-transcriptional mechanisms are a significant part of the process, with p53 translocation from the cytosol into the nucleus of copper-treated cells. Treatment of Hep G2 cells with increasing concentrations of the copper chelator tetraethylenepentamine (TEPA, 0-50 micromol/L, 48 h) reduced cellular copper and increased mean p53 mRNA abundance by over fourfold with nuclear translocation of the wild-type protein. However, TEPA treatment did not result in a loss of cell viability or appear to induce apoptosis.

In vivo evidence for accelerated generation of hydroxyl radicals in liver of Long-Evans Cinnamon (LEC) rats with acute hepatitis

The Long-Evans Cinnamon (LEC) rats accumulate excess copper (Cu) in the liver in a manner similar to patients with Wilson's disease (WD) and spontaneously develop acute hepatitis with severe jaundice. Although hydroxyl radicals (*OH) have been proposed to be a cause of hepatitis by the accumulation of Cu, it is not clear whether or not *OH can be produced in the liver of hepatitic LEC rats in vivo and also can be involved in the onset of hepatitis. In the present study, *OH production in plasma and liver of hepatitic LEC rats was quantified by trapping *OH with salicylic acid (SA) as 2, 3-dihydroxybenzoic acid (2, 3-DHBA). The ratios of 2, 3-DHBA/SA were significantly higher in plasma and liver of hepatitic LEC rats than those of Wistar rats and LEC rats showing no signs of hepatitis. Furthermore, the ratios of 2, 3-DHBA/SA in plasma and liver of hepatitic LEC rats were almost the same as those of Wistar rats treated orally with CuSO(4) (0.5 mmol/kg) 2 h before acetylsalicylic acid (ASA) injection. We also evaluated the protective effects of D-mannitol (a *OH scavenger) treatment against acute hepatitis in LEC rats. D-mannitol (500 mg/kg) was administered intraperitoneally to 10-week-old LEC rats for 3 weeks. D-mannitol treatment suppressed the increases in serum aspartate aminotransferase activity and total bilirubin concentration. In addition, D-mannitol treatment significantly reduced hepatic mitochondrial lipid peroxidation, which is thought to be important in the pathogenesis of Cu-induced hepatotoxicity. These observations suggest that accelerated generation of *OH catalyzed by free Cu in the liver may, at least in part, play a role in the pathogenesis of acute hepatitis in LEC rats.

The antioxidant effect of DL-alpha-lipoic acid on copper-induced acute hepatitis in Long-Evans Cinnamon (LEC) rats

The Long-Evans Cinnamon (LEC) rats, due to a genetic defect, accumulate excess copper (Cu) in the liver in a manner similar to patients with Wilson's disease and spontaneously develop acute hepatitis with severe jaundice. In this study we examined the protective effect of DL-alpha-Lipoic acid (LA) against acute hepatitis in LEC rats. LA was administered to LEC rats by gavage in doses of 10, 30 and 100 mg/kg five times per week, starting at 8-weeks-old and continuing till 12-weeks-old. Although LA had little effect against the increases in serum transaminase activities, it suppressed the loss of body weight and prevented severe jaundice in a dose-dependent manner. Antioxidant system analyses in liver showed that LA treatment significantly suppressed the inactivations of catalase and glutathione peroxidase, and the induction of heme oxygenase-1, an enzyme which is inducible under oxidative stress. Furthermore, LA showed dose-dependent suppressive effect against increase in nonheme iron contents of both cytosolic and crude mitochondrial fractions in a dose-dependent manner. Although at the highest dose, LA slightly suppressed the accumulation of Cu in crude mitochondrial fraction, it had no effect on the accumulation of Cu in cytosolic fraction. While LA completely suppressed the increase in lipid peroxidation (LPO) in the microsomal fraction at the highest dose, the suppressive effect against LPO in crude mitochondrial fractions was slight. From these results, it is concluded that LA has antioxidant effects at the molecular level against the development of Cu-induced hepatitis in LEC rats. Moreover, mitochondrial oxidative damage might be involved in the development of acute hepatitis in LEC rats.

Increased p53 mutation load in nontumorous human liver of wilson disease and hemochromatosis: oxyradical overload diseases

Hemochromatosis and Wilson disease (WD), characterized by the excess hepatic deposition of iron and copper, respectively, produce oxidative stress and increase the risk of liver cancer. Because the frequency of p53 mutated alleles in nontumorous human tissue may be a biomarker of oxyradical damage and identify individuals at increased cancer risk, we have determined the frequency of p53 mutated alleles in nontumorous liver tissue from WD and hemochromatosis patients. When compared with the liver samples from normal controls, higher frequencies of G:C to T:A transversions at codon 249 (P < 0.001) and C:G to A:T transversions and C:G to T:A transitions at codon 250 (P < 0.001 and P < 0.005) were found in liver tissue from WD cases, and a higher frequency of G:C to T:A transversions at codon 249 (P < 0.05) also was found in liver tissue from hemochromatosis cases. Sixty percent of the WD and 28% of hemochromatosis cases also showed a higher expression of inducible nitric oxide synthase in the liver, which suggests nitric oxide as a source of increased oxidative stress. A high level of etheno-DNA adducts, formed from oxyradical-induced lipid peroxidation, in liver from WD and hemochromatosis patients has been reported previously. Therefore, we exposed a wild-type p53 TK-6 lymphoblastoid cell line to 4-hydroxynonenal, an unsaturated aldehyde involved in lipid peroxidation, and observed an increase in G to T transversions at p53 codon 249 (AGG to AGT). These results are consistent with the hypothesis that the generation of oxygen/nitrogen species and unsaturated aldehydes from iron and copper overload in hemochromatosis and WD causes mutations in the p53 tumor suppressor gene.

Copper-induced apical trafficking of ATP7B in polarized hepatoma cells provides a mechanism for biliary copper excretion

BACKGROUND & AIMS

Mutations in the ATP7B gene, encoding a copper-transporting P-type adenosine triphosphatase, lead to excessive hepatic copper accumulation because of impaired biliary copper excretion in Wilson's disease. In human liver, ATP7B is predominantly localized to the trans-Golgi network, which appears incompatible with a role of ATP7B in biliary copper excretion. The aim of this study was to elucidate this discrepancy.

METHODS

Immunofluorescence and electron-microscopic methods were used to study the effects of excess copper on ATP7B localization in polarized HepG2 hepatoma cells.

RESULTS

ATP7B is localized to the trans-Golgi network only when extracellular copper concentration is low (<1 micromol/L). At increased copper levels, ATP7B redistributes to vesicular structures and to apical vacuoles reminiscent of bile canaliculi. After copper depletion, ATP7B returns to the trans-Golgi network. Brefeldin A and nocodazole impair copper-induced apical trafficking of ATP7B and cause accumulation of apically retrieved transporters in a subapical compartment, suggesting continuous recycling of ATP7B between this vesicular compartment and the apical membrane when copper is increased.

CONCLUSIONS

Copper induces trafficking of its own transporter from the trans-Golgi network to the apical membrane, where it may facilitate biliary copper excretion. This system of ligand-induced apical sorting provides a novel mechanism to control copper homeostasis in hepatic cells.

The level of serum lipids, vitamin E and low density lipoprotein oxidation in Wilson's disease patients

The aim of this study was to estimate the level of lipids and of the main serum antioxidant, alpha-tocopherol (vitamin E), and to evaluate the susceptibility of low density lipoprotein (LDL) to oxidation in Wilson's disease patients. It was assumed that enhanced LDL peroxidation caused by high copper levels could contribute to the injury of liver and other tissues. The group investigated comprised 45 individuals with Wilson's disease treated with penicillamine or zinc salts and a control group of 36 healthy individuals. Lipids were determined by enzymatic methods, alpha-tocopherol by high performance liquid chromatography, the susceptibility of LDL to oxidation in vitro by absorption changes at 234 nm during 5 h and end-products of LDL lipid oxidation as thiobarbituric acid reacting substances. In Wilson's disease patients total cholesterol, LDL cholesterol and alpha-tocopherol levels were significantly lower compared with the control group. No difference in LDL oxidation in vitro between the patients and the controls was stated.

CONCLUSION

enhanced susceptibility of isolated LDL for lipid peroxidation in vitro was not observed in Wilson's disease patients. One cannot exclude, however, that because of low alpha-tocopherol level lipid peroxidation in the tissues can play a role in the pathogenesis of tissue injury in this disease.

Starvation impairs antioxidant defense in fatty livers of rats fed a choline-deficient diet

Although fatty liver (FL) is considered an innocuous condition, the frequent incidence of graft failure when FL are transplanted has renewed interest in the intracellular disorders causative of or consequent to fatty degeneration. Oxidative stress and nutritional status modulate the tolerance to reperfusion injury in control livers (CL), but very little is known in the case of FL. This study was designed to compare the oxidative balance in CL and FL from fed and food-deprived rats. Serum and liver samples were collected from fed and starved (18 h) rats with CL or FL induced by a choline-deficient diet. Hepatic injury was assessed by transaminase activities and histology. The hepatic concentrations of glutathione (GSH), vitamin C, alpha-tocopherol, thiobarbituric acid-reactive substances (TBARS) and protein carbonyls (PC) were measured. Fed rats with FL had significantly greater TBARS and lower alpha-tocopherol and vitamin C levels than those with CL, whereas GSH and PC concentrations were not affected. Starvation impaired the oxidative balance in both groups. However, compared with the other groups, FL from food-deprived rats generally had the lowest hepatic concentrations of alpha-tocopherol, vitamin C and GSH. Unlike in CL, protein oxidation occurred in FL. These data indicate that fatty liver induced by consumption of a choline-deficient diet is associated with a lower level of antioxidants, which results in lipid peroxidation. Starvation further affects these alterations and extends the damage to proteins. In conclusion, steatosis and starvation may act synergistically on the depletion of antioxidants, predisposing fatty livers to a reduced tolerance to oxidative injury.

Oxidative-phosphorylation defects in liver of patients with Wilson's disease

BACKGROUND

Wilson's disease (WD) is caused by mutations in a P-type ATPase and is associated with copper deposition in liver and brain. The WD protein is present in the trans-Golgi network and may also be imported into mitochondria. The WD protein functions as a P-type copper transporting ATPase in the Golgi but any action in mitochondria is at present unknown.

METHODS

We studied mitochondrial function and aconitase activity in WD liver tissue and compared the results with those in a series of healthy controls and patients without WD.

FINDINGS

There was evidence of severe mitochondrial dysfunction in the livers of patients with WD. Enzyme activities were decreased as follows: complex I by 62%, complex II+III by 52%, complex IV by 33%, and aconitase by 71%. These defects did not seem to be secondary to penicillamine use, cholestasis, or poor hepatocellular synthetic function.

INTERPRETATION

The results show that there is a defect of energy metabolism in WD. The pattern of enzyme defects suggests that free-radical formation and oxidative damage, probably mediated via mitochondrial copper accumulation, are important in WD pathogenesis. These results provide a rationale for a study of the use of antioxidants in WD.

Accumulation of copper in the liver and hepatic injury in chronic hepatitis C

BACKGROUND AND AIMS

Relationships between chronic liver disease and trace metals have not been clearly understood. To examine connections between severity of hepatic fibrosis in chronic hepatitis C and copper, iron and zinc we measured the contents of these metals in liver tissue and serum in the patients.

METHODS

Forty-one patients (26-62 years), 13 with fibrosis representing grade F1, 16 with F2, seven with F3, and five with F4, entered this study. Metals were quantified in needle liver-biopsy specimens by particle-induced X-ray emission. In serum, metals were measured by flameless atomic absorption spectrometry.

RESULTS

Hepatic copper content increased with progression of hepatic fibrosis (P < 0.05). The copper content correlated positively with bilirubin (r = 0.466, P = 0.0023), and with type IV collagen (r = 0.402, P = 0.0086) and correlated negatively with albumin (r = -0.404, P = 0.080). However, hepatic iron and zinc contents did not show a significant differences between grades of fibrosis.

CONCLUSIONS

Copper accumulation in fibrotic livers caused by chronic hepatitis C may contribute to hepatic injury. The real mechanism is not known at present, but excess copper may damage the liver by oxidative stress.

Pathogenesis of liver fibrosis: role of oxidative stress

In the liver, the progressive accumulation of connective tissue, a complex and dynamic process termed fibrosis, represents a very frequent event following a repeated or chronic insult of sufficient intensity to trigger a "wound healing"-like reaction. The fibrotic process recognises the involvement of various cells and different factors in bringing about an excessive fibrogenesis with disruption of intercellular contacts and interactions and of extracellular matrix composition. However, Kupffer cells, together with recruited mononuclear cells, and hepatic stellate cells are by far the key-players in liver fibrosis. Their cross-talk is triggered and favoured by a series of chemical mediators, with a prominent role played by the transforming growth factor beta. Both expression and synthesis of this inflammatory and pro-fibrogenic cytokine are mainly modulated through redox-sensitive reactions. Further, involvement of reactive oxygen species and lipid peroxidation products can be clearly demonstrated in other fundamental events of hepatic fibrogenesis, like activation and effects of stellate cells, expression of metalloproteinases and of their specific inhibitors. The important outcome of such findings as regards the pathogenesis of liver fibrosis derives from the observation of a consistent and marked oxidative stress condition in many if not all chronic disease processes affecting hepatic tissue. Hence, reactive oxidant species likely contribute to both onset and progression of fibrosis as induced by alcohol, viruses, iron or copper overload, cholestasis, hepatic blood congestion.

Superoxide dismutase activity in children with chronic liver diseases

BACKGROUND/AIMS

Liver disease in infancy has multiple etiologies. As reactive oxygen intermediates are involved in several types of tissue damage, we have investigated whether different forms of liver disease in infancy are associated with increased free radical generation, using an indirect approach in which superoxide dismutase (a free radical scavenger) activity is determined in the liver tissue.

METHODS

A total of 48 liver biopsies performed at diagnosis were evaluated retrospectively. Nine infants had biliary atresia, eight Alagille syndrome, seven alantitrypsin deficiency and 12 cryptogenic hepatitis. As controls we studied 12 biopsies with normal histology obtained from seven children with portal vein thrombosis and five children who underwent biopsy for management reason but had no liver disease. Superoxide dismutase activity in liver biopsy specimens was measured using the cytochrome C method by spectrophotometry and expressed as U SOD/mg protein.

RESULTS

Superoxide dismutase activity was significantly increased in biliary atresia (1.25 +/- 0.56 U SOD/mg protein, p<0.0001) and Alagille syndrome (1.31 +/- 0.56 U SOD/mg protein, p<0.0001) as compared with al-antitrypsin deficiency (0.75 +/- 0.3 U SOD/mg protein), neonatal hepatitis (0.72 +/- 0.37 U. SOD/mg protein) and normal controls (0.4 +/- 0.7 U. SOD/mg protein). The highest level of SOD activity was found, however, in control children with portal vein thrombosis (2.09 +/- 0.96 U SOD/mg protein; p<0.0001 as compared to the other groups).

CONCLUSION

Superoxide dismutase, a key enzyme in free radical protection, is increased significantly in the liver tissue of infants with cholestatic liver disease due to bile duct damage and in children with portal vein thrombosis, suggesting that products of free radical reactions are involved in the pathogenesis of these disorders.

Regulation of mitochondrial cytochrome b mRNA by copper in cultured human hepatoma cells and rat liver

Copper overload and deficiency are known to cause morphological and functional mitochondrial abnormalities. The reverse transcriptase-polymerase chain reaction (RT-PCR)-based method of differential display of mRNA was used to identify genes with altered expression in cultured human hepatoma cells (Hep G2) exposed to increasing concentrations of copper (0-100 microM, 24 h). Copper regulation of a cloned PCR product, identified as the gene for the mitochondrially encoded cytochrome b, was confirmed by Northern analysis and in situ hybridization. Copper toxicity increased cytochrome b mRNA abundance up to 3.6-fold, and copper chelation reduced it by 50%. Hepatic cytochrome b mRNA was also increased in rats fed a high-copper diet. Thapsigargin treatment resulted in a significant increase in cytochrome b mRNA, suggesting that an increase in intracellular calcium may be involved in the mechanism of copper action. Furthermore, although cyclohexamide (CHX) alone did not increase cytochrome b mRNA, the addition of CHX and copper resulted in a sixfold increase. These data suggest a role for cytochrome b in the response to increases or decreases in hepatic copper.

Mitochondrial respiratory chain disorders and the liver

Mitochondrial respiratory chain disorders are an established cause of liver failure in early childhood but they are probably under-diagnosed, partly due to under-recognition and partly due to the difficulty of investigation. It is particularly important to look for mitochondrial disorders if the liver disease presents with hypoglycaemia and lactic acidaemia or if it is accompanied by neurological, muscle or renal tubular abnormalities. Respiratory chain defects have been demonstrated in a number of patients who die of liver failure following severe epilepsy; this includes at least some cases of Alpers syndrome or 'progressive neuronal degeneration of childhood'. In mitochondrial liver disease, histology usually shows steatosis, often accompanied by fibrosis, cholestasis and loss of hepatocytes. Unless the clinical picture suggests a particular syndrome, such as Pearson syndrome, biochemical assays and histochemistry should be the initial investigations. Ideally, investigations should be carried out on liver as well as more standard tissues, such as muscle, since defects can be tissue-specific. Nuclear defects and mtDNA point mutations are probably responsible for many cases of mitochondrial liver disease but, as yet, the only identified molecular abnormalities are mtDNA rearrangements and mtDNA depletion. Treatment of mitochondrial liver disease is unsatisfactory. If the disease is confined to the liver, transplantation may be appropriate but in several patients transplantation has been followed by the appearance of disease in other organs, particularly the brain.

An update on the role of free radicals and antioxidant defense in human disease

Mounting clinical and experimental evidence indicates that free radicals play important roles in many physiological and pathological conditions. The wider application of free radical measurement has increased awareness of functional implications of radical-induced impairment of the oxidative/antioxidative balance. In the following review, the role of oxygen free radicals in some human and experimental pathological conditions is described, with particular emphasis on the mechanisms by which they produce oxidative damage to lipids, proteins, and nucleic bases. The role of free radicals and the activation of the antioxidant systems in arteriosclerosis and ageing, diabetes, ischemia/reperfusion injury, ethanol intoxication, and liver steatosis is discussed. Therapeutic approaches to the use of antioxidants have been described and prospects for clinical use have been considered.

Zinc therapy increases duodenal concentrations of metallothionein and iron in Wilson's disease patients

OBJECTIVE

Wilson's disease is effectively treated by zinc administration which, in vitro, increases metallothionein concentrations. To ascertain whether the latter also occurs in humans we measured metallothionein and trace element concentrations in the duodenal mucosa of 15 Wilson's disease patients: 12 treated with zinc sulphate, two treated with penicillamine, and one not yet on treatment. The control group consisted of 17 patients with dyspepsia, who underwent the same study protocol.

METHODS

Metallothionein and trace element concentrations were measured in duodenal mucosa biopsies according to the silver-saturation hemolysate method and atomic absorption spectrophotometry.

RESULTS

Metallothionein concentrations increased by 1500% after zinc and 150% after penicillamine in Wilson's disease patients, with respect to controls who had negative endoscopy and Wilson's disease patients who were not treated. A significant correlation was found between metallothionein and duodenal zinc concentrations. Mucosal iron concentration increased in Wilson's disease patients whether they were treated with zinc or penicillamine. Duodenum with duodenitis also had significantly increased iron levels compared with normal duodenum.

CONCLUSIONS

Zinc administration increases intestinal metallothionein in Wilson's disease patients. The blockade of copper absorption and its elimination in the stools on desquamation of the intestinal cells probably explains one of the mechanisms underlying the effect of zinc treatment. Despite normal endoscopy, Wilson's disease patients present increased mucosal iron concentrations similar to those in controls with duodenitis. Metallothionein may therefore prevent oxidative damage caused by metal toxicity.

Mitochondria and childhood liver diseases

The newly recognized mitochondrial hepatopathies should be considered in the differential diagnosis of acute and chronic liver disease in childhood. It may appear as neonatal liver failure, delayed onset liver failure in early childhood or as a multisystemic process. Comparison of features of several of the known primary mitochondrial hepatopathies is provided in Table 5. Secondary mitochondrial hepatopathies are examples of the critical importance of mitochondrial function in the pathogenesis of liver injury. Our improved understanding of the role of the mitochondria in cellular necrosis and apoptosis opens the way for development of new therapeutic approaches to several hepatic disorders. Primary mitochondrial hepatopathies (especially the respiratory chain defects) should be considered in any child with liver disease and neuromuscular involvement, multisystemic disease, lactic acidosis or rapidly progressive disease, and when hepatic steatosis is the dominant histologic finding on examination of a liver specimen. Current therapies are inadequate; improved therapeutic strategies are needed for these disorders. Some patients with respiratory chain defects limited to the liver have had successful liver transplantation. This field is in evolution and will undoubtedly provide new and important developments as the next millennium begins.

The effect of idebenone, a coenzyme Q analogue, on hydrophobic bile acid toxicity to isolated rat hepatocytes and hepatic mitochondria

Oxidant stress induced by hydrophobic bile acids has been implicated in the pathogenesis of liver injury in cholestatic liver disorders. We evaluated the effect of idebenone, a coenzyme Q analogue, on taurochenodeoxycholic acid (TCDC)-induced cell injury and oxidant stress in isolated rat hepatocytes and on glycochenodeoxycholic acid (GCDC)-induced generation of hydroperoxides in fresh hepatic mitochondria. Isolated rat hepatocytes in suspension under 9% oxygen atmosphere were preincubated with 0, 50, and 100 micromol/l idebenone for 30 min and then exposed to 1000 micromol/l TCDC for 4 h. LDH release (cell injury) and thiobarbituric acid reactive substances (measure of lipid peroxidation) increased after TCDC exposure but were markedly suppressed by idebenone pretreatment. In a second set of experiments, the addition of 100 micromol/l idebenone up to 3 h after hepatocytes were exposed to 1000 micromol/l TCDC resulted in abrogation of subsequent cell injury and markedly reduced oxidant damage to hepatocytes. Chenodeoxycholic acid concentrations increased to 5.15 nmol/10(6) cells after 2 h and to 7.05 after 4 h of incubation of hepatocytes with 1000 micromol/l TCDC, and did not differ in the presence of idebenone. In freshly isolated rat hepatic mitochondria, when respiration was stimulated by succinate, 10 micromol/l idebenone abrogated the generation of hydroperoxides during a 90-minute exposure to 400 micromol/l GCDC. These data demonstrate that idebenone functions as a potent protective hepatocyte antioxidant during hydrophobic bile acid toxicity, perhaps by reducing generation of oxygen free radicals in mitochondria.

Wilson disease

Wilson disease is a recessively inherited disorder of copper transport. Clinical features are highly variable, with any combination of neurological, hepatic or psychiatric illness. The age of onset varies from 3 to 50 years of age. Diagnosis is challenging because no specific combination of clinical or biochemical features is necessarily definitive. The genetic defect is due to a variety of abnormalities in a copper-transporting membrane ATPase. Most of the more than 80 mutations are present at a low frequency, and mutations differ between ethnic groups. At least two mutations are sufficiently common to aid in rapid diagnosis, in European and Asian populations respectively. Molecular analysis can provide a definitive diagnosis for asymptomatic sibs. Treatment, using chelating agents or zinc, is most effective when started before permanent tissue damage occurs.

Wilson's disease

Wilson's disease is an autosomal, recessive-inherited disorder of impaired biliary copper excretion that results in the accumulation of copper in various organs including the liver, the cornea and the brain. The Wilson's disease gene on chromosome 13 codes for a copper transporting P-type ATPase-ATP7B. More than 60 mutations of this gene have been described. The diagnosis of Wilson's disease is based on clinical findings and laboratory abnormalities and can be made if two of the following symptoms are present: Kayser-Fleischer rings; topical neurologic symptoms; and low serum ceruloplasmin levels. In less typical cases diagnosis requires various other tests of copper metabolism. Effective medical treatment with copper chelators (D-penicillamine, trientine) or zinc results in symptomatic improvement and normal life expectancy. Orthotopic liver transplantation is indicated in advanced cases with hepatic decompensation or in patients with fulminant Wilson's disease.

Review: molecular approaches to inherited liver disease. Focus on Wilson disease

Although infectious agents account for a large proportion of liver disease, inherited forms of liver disease, often treatable, must not be overlooked. New approaches to the cloning of disease genes are allowing an increased understanding of the basic defect of human diseases. Identification of disease genes can have practical applications for diagnosis, can provide information on prognosis and can lead to new therapies. This review focuses on selected inherited liver diseases and the knowledge to be gained from molecular studies. Three genetic diseases affecting the liver, Wilson disease, haemochromatosis and alpha 1-antitrypsin deficiency, are selected as examples of current approaches to the study of genetic liver disease.

Oxidative damage and fibrogenesis

Various chronic disease processes are characterized by progressive accumulation of connective tissue under-going fibrotic degeneration. Evidence of oxidative reactions is often associated with fibrogenesis occurring in liver, lung, arteries, and nervous system. Moreover, an increasing bulk of experimental and clinical data supports a contributory role of oxidative stress in the pathogenesis of this kind of disease. Indeed, many etiological agents of fibrogenesis stimulate free radical reactions either directly or through inflammatory stimuli. Free radicals, as well as products of their reaction with biomolecules, appear to modulate the activity of the two cellular types mainly involved in the process, namely phagocytes and extracellular matrix-producing cells. Lipid peroxidation and certain lipid peroxidation products induce genetic overexpression of fibrogenic cytokines, the key molecules in the pathomechanisms of fibrosis, as well as increased transcription and synthesis of collagen. Both these events can be downregulated, at least in experimental models, by the use of antioxidants. The effect of oxidative stress on cytokine gene expression appears to be an important mechanism by which it promotes connective tissue deposition.

Retrorsine in breast milk influences copper handling in suckling rat pups

AIMS

To explore the hypothesis that a second xenobiotic agent is required with excess copper to produce Indian Childhood Cirrhosis, this study investigated the effect of the pyrrolizidine alkaloid retrorsine fed to the mother during the suckling period upon the serial changes in neonatal copper status.

METHODS

Female Wistar rats with new-born litters were fed either a control or a retrorsine (50 mg/kg) diet. At 0, 4, 8, 11, 15, 18 and 21 days, pups from each litter were weighed, sacrificed and their livers removed for copper, DNA and metallothionein analysis. Serum samples were assayed for caeruloplasmin oxidase activity and albumin.

RESULTS

1) Higher than adult level of hepatic copper in normal rats which rose post-natally before declining from day 11 after birth, 2) raised hepatic copper concentrations and total copper in the retrorsine group from day 15; levels were higher than adult at birth, 3) reduced serum caeruloplasmin oxidase activity and albumin levels in retrorsine group, but both groups lower than adult, 4) lower hepatic metallothionein levels in retrorsine group, but both groups higher than adult, and 5) reduced liver DNA in the retrorsine group when expressed as total DNA and per gram of tissue. These changes were not secondary to under-nutrition as a small study on under-nourished rat neonates showed that copper handling is not significantly altered when compared to well-nourished rats.

CONCLUSIONS

Retrorsine passing to rat neonates via breast milk causes: 1) the accumulation of hepatic copper, 2) impairment of the rise in serum caeruloplasmin, which could indicate a decline in synthesis or failure of copper incorporation into the apo-protein, 3) a decrease in hepatic metallothionein and serum albumin levels, again suggesting diminished protein synthesis, and 4) reduced hepatic DNA indicative of decreased cell number but increased cell size. Accumulation of liver copper but reduction of copper-binding proteins could result in free copper and explain the synergistic hepatotoxicity of copper and retrorsine.

Isoprostanes--prostaglandin-like compounds formed in vivo independently of cyclooxygenase: use as clinical indicators of oxidant damage

F2-isoprostanes are prostanoids produced independently of cyclooxygenase by free radical-catalyzed peroxidation of arachidonic acid-containing lipids. Quantification of F2-isoprostanes from biologic fluids and tissues represents an important advance in the detection and measurement of lipid peroxidation in vivo. In addition, efforts to understand both the biophysical effects of isoprostane containing lipids and the biologic effects of free isoprostanes should lead to a better understanding of the mechanisms responsible for oxidant stress-related alterations in homeostasis. Continued application of F2-isoprostane measurement in experimental models of free radical-induced injury and human disease may allow better design and evaluation of antioxidant therapeutic strategies.

Antioxidants in pediatric gastrointestinal disease

Oxidant stress seems to be involved in the pathogenesis of several important gastroenterologic disorders in infants and children. The question can still be asked, in most circumstances, whether the oxidant stress precedes, and therefore is involved in, tissue or cellular injury or is a result of injury and not of clinical importance. The data favor the former situation in several inflammatory conditions of the bowel and in a variety of liver diseases. Experimental and clinical testing of this possible basic mechanism of tissue injury over the next few years will shed light on the role of antioxidants in treating gastrointestinal disorders.

alpha-tocopherol ameliorates oxidant injury in isolated copper-overloaded rat hepatocytes

The objective of this study was to determine the role of oxidant stress in cell injury produced by in vivo copper overload of isolated rat hepatocytes. Rats were maintained on diets with elevated or normal copper content, and hepatocytes were isolated and then incubated for 4 h in physiologic buffer at physiologic oxygen saturations. In hepatocytes from copper-overloaded rats, a significant loss of cell viability (trypan blue exclusion) over 4 h compared with control cells was associated with a significant increase in lipid peroxidation (thiobarbituric acid-reacting substances). Incubation of copper-overloaded hepatocytes with the copper chelator, 2,3,2-tetramine, had a partial protective effect. Incubation with D-alpha-tocopheryl succinate completely ameliorated the copper-induced changes in viability and lipid peroxidation. We conclude that antioxidants may protect the isolated hepatocyte from copper toxicity and should be explored as potential therapeutic agents in states of copper overload.