Copper metabolism leading to and following acute hepatitis in LEC rats

Rapid and reliable diagnosis of Wilson disease using X-ray fluorescence

Wilson's disease (WD) is a rare autosomal recessive disease due to mutations of the gene encoding the copper-transporter ATP7B. The diagnosis is hampered by the variability of symptoms induced by copper accumulation, the inconstancy of the pathognomonic signs and the absence of a reliable diagnostic test. We investigated the diagnostic potential of X-ray fluorescence (XRF) that allows quantitative analysis of multiple elements. Studies were performed on animal models using Wistar rats (n = 10) and Long Evans Cinnamon (LEC) rats (n = 11), and on human samples including normal livers (n = 10), alcohol cirrhosis (n = 8), haemochromatosis (n = 10), cholestasis (n = 6) and WD (n = 22). XRF experiments were first performed using synchrotron radiation to address the elemental composition at the cellular level. High-resolution mapping of tissue sections allowed measurement of the intensity and the distribution of copper, iron and zinc while preserving the morphology. Investigations were further conducted using a laboratory X-ray source for irradiating whole pieces of tissue. The sensitivity of XRF was highlighted by the discrimination of LEC rats from wild type even under a regimen using copper deficient food. XRF on whole formalin-fixed paraffin embedded needle biopsies allowed profiling of the elements in a few minutes. The intensity of copper related to iron and zinc significantly discriminated WD from other genetic or chronic liver diseases with 97.6% specificity and 100% sensitivity. This study established a definite diagnosis of Wilson's disease based on XRF. This rapid and versatile method can be easily implemented in a clinical setting.

Evolution of exchangeable copper and relative exchangeable copper through the course of Wilson's disease in the Long Evans Cinnamon rat

BACKGROUND

Wilson's disease (WD) is an inherited disorder of copper metabolism leading to liver failure and/or neurological impairment. Its diagnosis often remains difficult even with genetic testing. Relative exchangeable copper (REC) has recently been described as a reliable serum diagnostic marker for WD.

METHODOLOGY/PRINCIPAL FINDINGS

The aim of this study was to validate the use of REC in the Long Evans Cinnamon (LEC) rat, an animal model for WD, and to study its relevance under different conditions in comparison with conventional markers. Two groups of LEC rats and one group of Long-Evans (LE) rats were clinically and biologically monitored from 6 to 28 weeks of age. One group of LEC rats was given copper-free food. The other groups had normal food. Blood samples were collected each month and different serum markers for WD (namely ceruloplasmin oxidase activity, exchangeable copper (CuEXC), total serum copper and REC) and acute liver failure (serum transaminases and bilirubinemia) were tested. Every LEC rat under normal food developed acute liver failure (ALF), with 40% global mortality. Serum transaminases and bilirubinemia along with total serum copper and exchangeable copper levels increased with the onset of acute liver failure. A correlation was observed between CuEXC values and the severity of ALF. Cut-off values were different between young and adult rats and evolved because of age and/or liver failure. Only REC, with values >19%, was able to discriminate LEC groups from the LE control group at every time point in the study. REC sensitivity and specificity reached 100% in adults rats.

CONCLUSIONS/SIGNIFICANCE

REC appears to be independent of demographic or clinical data in LEC rats. It is a very simple and reliable blood test for the diagnosis of copper toxicosis owing to a lack of ATP7B function. CuEXC can be used as an accurate biomarker of copper overload.

The genotoxic, hepatotoxic, nephrotoxic, haematotoxic and histopathological effects in rats after aluminium chronic intoxication

Aluminium (Al) is used in water purification and is also present in several manufactured foods and medicines. Al is known to induce a broad range of physiological, biochemical and behavioural dysfunctions in laboratory animals and humans. This investigation was carried out to investigate the effects of subchronic exposure to Al (as AlCl3) in rats. Sprague-Dawley rats were randomly separated into two groups. Group 1 rats treated with sodium chloride served as the control, group 2 rats were treated with Al (as AlCl3, 5 mg/kg body weight) intraperitonally for 10 weeks. Animals were killed and blood samples were analyzed for blood serum alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) enzyme activities and creatinine, urea (U) and uric acid (UA) levels for evaluating hepatotoxicity and nephrotoxicity. Blood parameters including red blood cells (RBCs), haemoglobin (Hb) concentration, haematocrit (Ht), platelets (PLTs) and white blood cells (WBCs) were compared between control and experimental group to assess haematoxicity. In order to determine the genotoxicity, the number of micronucleated hepatocytes (MNHEPs) was counted in isolated hepatocytes. In addition, histological alterations in liver and kidney samples were investigated. After exposure with Al, the enzymatic activities of ALP, AST, ALT and LDH, and the levels of U and UA significantly increased. RBC, WBC, PLT, Hb and Ht revealed significant decreases in experimental group compared to the control. AlCl3 caused a significant increase in MNHEPs. Furthermore, severe pathological damages were established in both liver and kidney samples. Subchronic exposure to low doses of Al can produce serious dysfunctions in rat blood, liver and kidney, and exposure to this metal can result in greater damages.

The biogenic methanobactin is an effective chelator for copper in a rat model for Wilson disease

Copper is an essential redox-active metal ion which in excess becomes toxic due to the formation of reactive oxygen species. In Wilson disease the elevated copper level in liver leads to chronic oxidative stress and subsequent hepatitis. This study was designed to evaluate the copper chelating efficiency of the bacterial methanobactin (MB) in a rat model for Wilson disease. Methanobactin is a small peptide produced by the methanotrophic bacterium Methylosinus trichosporium OB3b and has an extremely high affinity for copper. Methanobactin treatment of the rats was started at high liver copper and serum aspartate aminotransferase (AST) levels. Two dosing schedules with either 6 or 13 intraperitoneal doses of 200mg methanobactin per kg body weight were applied. Methanobactin treatment led to a return of serum AST values to basal levels and a normalization of liver histopathology. Concomitantly, copper levels declined to 45% and 24% of untreated animals after 6 and 13 doses, respectively. Intravenous application of methanobactin led to a prompt release of copper from liver into bile and the copper was shown to be associated with methanobactin. In vitro experiments with liver cytosol high in copper metallothionein demonstrated that methanobactin removes copper from metallothionein confirming the potent copper chelating activity of methanobactin.

Propolis prevents aluminium-induced genetic and hepatic damages in rat liver

Aluminium is present in several manufactured foods and medicines and is also used in water purification. Therefore, the present experiment was undertaken to determine the effectiveness of propolis in modulating the aluminium chloride (AlCl(3)) induced genotoxicity and hepatotoxicity in liver of rats. Animals were assigned to 1 of 4 groups: control; 34 mg AlCl(3)/kg bw; 50mg propolis/kg bw; AlCl(3) (34 mg/kg bw) plus propolis (50mg/kg bw), respectively. Rats were orally administered their respective doses daily for 30 days. At the end of the experiment, rats were anesthetized and hepatocytes (HEP) were isolated for counting the number of micronucleated hepatocytes (MNHEPs). In addition, the levels of serum enzymes and histological alterations in liver were investigated. AlCl(3) caused a significant increase in MNHEPs, alkaline phosphatase, transaminases (AST and ALT) and lactate dehydrogenase (LDH). Furthermore, severe pathological damages such as: sinusoidal dilatation, congestion of central vein, lipid accumulation and lymphocyte infiltration were established in liver. On the contrary, treatment with propolis alone did not cause any adverse effect on above parameters. Moreover, simultaneous treatments with propolis significantly modulated the toxic effects of AlCl(3). It can be concluded that propolis has beneficial influences and could be able to antagonize AlCl(3) toxicity.

Effect of glutathione depletion on removal of copper from LEC rat livers by tetrathiomolybdate

Tetrathiomolybdate (TTM) is a powerful and selective copper (Cu) chelator that is used as a therapeutic agent for Wilson disease. TTM is the sole agent that can remove Cu bound to metallothionein (MT) in the livers of Long-Evans rats with a cinnamon-like coat color (LEC rats). However, the administration of excess TTM causes the deposition of Cu and molybdenum (Mo) in the liver. In the present study, the effect of hepatic glutathione (GSH) depletion on the removal of Cu from the livers of LEC rats was evaluated to establish an effective therapy by TTM. Pretreatment with l-buthionine sulfoximine (BSO), a depletor of GSH in vivo, reduced the amounts of Cu and Mo excreted into both the bile and the bloodstream, and increased the amounts of Cu and Mo deposited in the livers of LEC rats in the form of an insoluble complex 4h after the TTM injection. The results suggest that GSH depletion creates an oxidative environment in the livers of LEC rats, and the oxidative environment facilitates the insolubilization of Cu and Mo in the livers of LEC rats after the TTM injection. Therefore, the effect of TTM on the removal of Cu from the liver was reduced in the oxidized condition. Wilson disease patients and LEC rats develop liver injury caused by oxidative damage. From a clinical viewpoint, increasing in the GSH concentration is expected to enhance the effect of TTM.

Evaluation of distribution patterns for copper and zinc in metallothionein and superoxide dismutase in chronic liver diseases and hepatocellular carcinoma using high-performance liquid chromatography (HPLC)

It has been reported that the copper (Cu) content of hepatocytes increases in chronic liver diseases and small hepatocellular carcinoma (HCC). In cells, Cu exists mainly as Cu-metallothionein (MT) or Cu, zinc (Zn)-superoxide dismutase (SOD). In this study, we investigated the biochemical state of Cu in the hepatocytes of patients with HCC using high-performance liquid chromatography (HPLC). The subjects of present study were 23 patients with HCC who underwent liver resection. The cancerous tissue and non-cancerous hepatic parenchyma with chronic disease were analyzed. In addition, as a normal control, hepatic tissue was collected at autopsy from 13 patients with no liver disease. Each sample was diluted with buffer, chilled, homogenized, and centrifuged. The supernatant was fractionated using HPLC. The metal contents of each fraction were measured using a desktop-type inductively coupled plasma (ICP) emission spectrochemical analyzer. HPLC analysis showed that MT existed mainly as Zn-MT in the normal hepatic tissue. The case of Cu,Zn-MT was significantly greater than Zn-MT in the non-cancerous, but diseased hepatic parenchyma than in the normal hepatic tissue (p<0.01). In comparison with non-cancerous hepatic parenchyma, the Cu-MT in the cancerous section was significantly greater than the Cu,Zn-MT (p<0.01). The Cu content for MT was significantly higher in small HCC (<40 mm) (p<0.01), and the absence of Cu or Zn in the MT fraction was significantly more frequent in the large HCC (>or=40 mm) (p<0.01). The Cu and Zn content for SOD in the samples showed no significant difference. Increase in the Cu content in the cancerous hepatic tissue were, thought to be reflecting changes in the distribution of Cu in the MT fraction of hepatic tissues.

Phenomenon of Hepatic Overload of Copper in Mugil cephalus: Role of Metallothionein and Patterns of Copper Cellular Distribution

In this work we describe a phenomenon of accumulation of copper (Cu) in livers of a teleost fish commonly known as mullet, Mugil cephalus. High levels of Cu, up to 1936 microg/g wet weight were found. The high Cu levels seem not to be associated with environmental Cu contamination, since the fish were collected from widely separated regions with low Cu concentrations. Other fish species sharing the same environment did not show high levels of Cu. The accumulation of Cu in mullet was seen in liver and most of the hepatic Cu was located in the non-cytosolic fraction. The intrahepatic distribution of Cu in mullet seems to depend on the total Cu content in the liver; as the total liver burden of Cu rose, Cu was increasingly recovered from the non-cytosolic fraction. Metallothionein in hepatic cytosols from mullet contained the most Cu. However, the Cu concentration not bound to metallothionein rose when total cytosolic Cu increased; which show that metallothionein, particularly at higher Cu levels, is not the major hepatic Cu-binding protein in cytosols of mullet. This report shows mullet as a very useful model to study the accumulation of Cu in the liver, which may lead to a better understanding of cellular mechanisms which control Cu homeostasis.

Protection from spontaneous hepatocellular damage by N-benzyl-d-glucamine dithiocarbamate in Long-Evans Cinnamon rats, an animal model of Wilson's disease

The Long-Evans Cinnamon (LEC) rat is a mutant strain that accumulates excessive tissue copper (Cu) and models the clinical symptoms and biological features of Wilson's disease in humans. We compared the effects of three metal chelating agents, N-benzyl-d-glucamine dithiocarbamate (BGD), d-penicillamine (D-PEN), and triethylenetetramine (TETA), on the biliary and urinary excretions of Cu using LEC rats. The animals were treated ip with each chelating agent (1 mmol/kg body weight) and then the bile and urine samples were collected for 3 h. Because single treatment with BGD markedly stimulated biliary excretion of Cu, the protective effect of repeated BGD injection on spontaneous hepatocellular damage was further examined. Separate groups received two weekly injections of BGD starting at 11 weeks of age and were compared to saline-injected controls. Serum alanine aminotransferase (ALT) activity and bilirubin level were significantly increased in control LEC rats by 19 weeks of age and histopathological analysis demonstrated extensive hepatic damage in these rats. However, repeated BGD injections prevented the increases in serum ALT and bilirubin and blocked the histopathological changes in the liver. Furthermore, although Cu rapidly accumulated in the liver, kidney, spleen, and serum of control LEC rats during the test period, repeated BGD injection largely prevented these increases. These results indicate that BGD treatment is effective in blocking excessive Cu accumulation in LEC rats that, in turn, provides protection from spontaneous liver damage.

Inhibitory effects of trientine, a copper-chelating agent, on induction of DNA strand breaks in hepatic cells of Long-Evans Cinnamon rats

Effects of treatment with trientine, a specific copper-chelating agent, on accumulation of copper and induction of DNA strand breaks were investigated in Long-Evans Cinnamon (LEC) rats, an animal model for human Wilson's disease. Copper accumulated in the livers of LEC rats in an age-dependent manner from 4 to 13 weeks of age. When LEC rats were treated with trientine from 10 weeks of age, hepatic copper contents did not increase and were maintained at the same levels as those in 10-week-old LEC rats. When the amounts of DNA single-strand breaks (SSBs) were estimated by a comet assay, SSBs of DNA were induced in a substantial population of LEC rat hepatic cells around 8 weeks of age and the amounts of SSBs increased in an age-dependent manner from 8 to 15 weeks of age. When LEC rats were treated with trientine from 10 weeks of age, the observed number of cells with DNA damage decreased dramatically, suggesting that induction of SSBs of DNA was inhibited and/or SSBs were repaired during the period of treatment with trientine. The results show that treatment of LEC rats with trientine decreases the number of DNA strand breaks observed, although copper contents remain high in the liver.

Role of tumor necrosis factor-alpha in the development of spontaneous hepatic toxicity in Long-Evans Cinnamon rats

The objective of this study was to evaluate the potential role of TNF-alpha in the onset of acute hepatitis in the Long-Evans Cinnamon (LEC) rat, an animal model for inherited copper (Cu) toxicosis. In LEC rats, Cu is accumulated in the liver with age, and clinical signs of acute hepatitis were observed as, icterus, reduced body weight, nasal bleeding, dehydration, and reduced food intake at 12 weeks of age. Cellular changes such as apoptosis in the liver were evident in these rats with increasing age. Positive TNF-alpha and TNFR1 immunostainings were observed in hepatocytes and Kupffer cells in LEC rats. Hepatic levels of caspase-3 activity, TNF-alpha mRNA, and protein were also increased in LEC rats from 6 to 12 weeks of age as compared with control Long-Evans (LE) rats. The neutralization of TNF-alpha by passive immunization or the inhibition of caspase activity can block the apoptotic process initiated by TNF-alpha. In this study, we evaluated the effects of passive immunization of LEC rats with weekly administration of anti-rat TNF-alpha on Cu-induced acute hepatitis. This treatment resulted in a reduction of the percentage of apoptotic cells in the liver, decreased activity of caspase-3, and also in down-regulation of the TNF-alpha gene expression. Thus, these results suggest a major role for TNF-alpha on the pathogenesis of Cu-induced acute hepatitis in LEC rats.

Chronic exposure of HepG2 cells to excess copper results in depletion of glutathione and induction of metallothionein

Metallothionein (MT) and reduced glutathione (GSH) play an important role in the intracellular handling of copper by preventing the generation and favouring the removal of copper-derived free radicals. The present study addressed the changes in MT and GSH that follow chronic (2 or 5 weeks) exposure of human hepatoblastoma cells (HepG2) to excess copper. Copper treatment (100 microM, 2 weeks) led to a 28-fold elevation in intracellular copper. Concomitantly, cells exhibited a seven-fold increase in total MT and an increment in its saturation with copper from 45 to 86%. Around 38% of copper in the cytosolic fraction could be accounted for by MT. GSH equivalents were substantially lowered (to 37% of basal levels) in treated cells, with only part of it being accounted for by an increase in GSSG. Copper-treatment induced no changes in catalase or GSH-peroxidase activities but it was associated with a small reduction in SOD (20%) and GSH-reductase (26%) activities. Copper-loaded cells did not differ from controls in their basal oxidative tone; however, when exposed to tert-butylhydroperoxide they exhibited a markedly greater susceptibility to undergo both oxidative stress and cell lysis. It is proposed that chronic exposure of HepG2 cells to excess copper is accompanied by "adaptive changes" in GSH and MT metabolism that would render cells substantially more susceptibility to undergo oxidative stress-related cytotoxicity.

Roles of metallothionein in copper homeostasis: responses to Cu-deficient diets in mice

Metallothionein (MT) protects the body from both harmful non-essential and excessive essential metals. Copper (Cu) is an essential metal, and its concentration in the body is regulated at a constant level between excess and deficient ones. Cu accumulating in the livers of Wilson disease patients and its animal model, Long-Evans rats with a cinnamon-like coat color (LEC) rats, is in the form of Cu,Zn-MT, MT being an antioxidant. Contrary to the efficient production of MT in response to excessive accumulation of Cu in LEC rats, Cu-binding to MT only occurs marginally under normal conditions. However, the present study revealed that Cu binds to MT more with a severe Cu-deficiency. Namely, male C57BL/6J mice were fed a Cu-deficient diet (0.037 mg Cu/g) and deionized water containing trientine, and then the concentration and distribution of Cu were determined. It was suggested that the cessation of biliary excretion and limitation of the Cu supply to ceruloplasmin are the first responses on feeding of a Cu-deficient diet, followed by an increase in Cu-MT with maintenance of the Cu concentration in the liver. These results suggest that MT causes the recruitment of Cu in a Cu-deficient environment by sequestering Cu from degraded Cu-enzymes and delivering it to Cu chaperones.

Dissolution of copper-rich granules in hepatic lysosomes by D-penicillamine prevents the development of fulminant hepatitis in Long-Evans cinnamon rats

BACKGROUND/AIM

The Long-Evans cinnamon rat has a mutation homologous to the human Wilson disease gene, leading to gross copper accumulation and the development of hepatitis. D-penicillamine, a copper-chelating drug widely and efficiently used in treating Wilson disease, has also been shown to prevent hepatitis in Long-Evans cinnamon rats. The objectives of this study were: i) to investigate the effectiveness of D-penicillamine when administered to the already affected animals, and ii) to elucidate the mechanism of action of the drug.

METHODS

Long-Evans cinnamon rats were divided into groups according to age and treatment with D-penicillamine. The drug was administered orally before and after the onset of hepatitis. Livers were examined by light and electron microscopy. The effect of D-penicillamine on the subcellular distribution and binding of copper was investigated in more detail. Finally, the interaction between D-penicillamine and specific hepatic copper-binding proteins was studied in vitro.

RESULTS

D-penicillamine when given to either healthy or diseased animals prevented or reversed hepatitis, respectively. The drug particularly inhibited the disease-specific accumulation of copper in lysosomes of hepatocytes, tissue macrophages and Kupffer cells. When administered to diseased animals, the drug sequestered copper particularly from insoluble lysosomal particles. According to results obtained in vitro, the mobilization of this copper is likely to proceed through the solubilization of these particles. In contrast and as supported by the in vitro data, D-penicillamine had only a minor effect on copper bound to metallothionein in the cytosol.

CONCLUSION

Our findings on the Long-Evans cinnamon rat provide some conclusions on the mechanism of action of D-penicillamine in Wilson disease therapy. The drug prevents the formation or promotes the solubilization of copper-rich particles which occur in lysosomes of hepatocytes and Kupffer cells in the livers of patients with Wilson disease. Once chelated with D-penicillamine copper might then be excreted into urine. However, the mobilization of copper by D-penicillamine seems to be limited due to the binding of the metal to metallothionein in liver cytosol. This copper, even at relatively high concentrations, apparently may be well tolerated.

Metabolic fate of the insoluble copper/tetrathiomolybdate complex formed in the liver of LEC rats with excess tetrathiomolybdate

Copper (Cu) accumulating in a form bound to metallothionein (MT) in the liver of Long-Evans rats with a cinnamon-like coat color (LEC rats), an animal model of Wilson disease, can be removed from the MT with tetrathiomolybdate (TTM). However, the insoluble Cu/TTM complex formed with excess TTM is known to be deposited in the liver. The metabolic fate of the insoluble Cu/TTM complex was investigated in the present study. LEC rats were injected with TTM at the dose of 10 mg/kg body weight for 8 consecutive days and were fed with a standard or low Cu diet for 14 days after the last injection. About 95% of the Cu in the liver became insoluble together with Mo. The concentration of Cu in the liver supernatants of rats fed with the standard diet increased significantly compared with that in rats dissected 24 h after the last injection (control rats), while the concentration in rats fed with the low Cu diet remained at a comparable level to that in the controls. The rate of Cu accumulation in the livers of rats fed with the standard diet did not differ before and after the treatment, suggesting that there was no rebound effect by treatment with TTM. These results suggest that the insoluble Cu/TTM complex is resolubilized in the liver, and that the solubilized complex is excreted into the bile and blood, i.e., the insoluble Cu/TTM complex is not the source of Cu re-accumulation in the form bound to MT in the liver after TTM treatment. It was concluded that, once Cu is complexed with TTM, the metal is excreted either immediately in the soluble form or slowly in the insoluble form into the bile and blood.

Identification of the zinc-binding protein specifically present in male rat liver as carbonic anhydrase III

A zinc (Zn)-binding protein that is present specifically in the livers of male adult rats was detected by HPLC with in-line detection by mass spectrometry (ICP MS). The Zn-binding protein was purified on Sephadex G-75 and G3000SW HPLC columns. and was identified as carbonic anhydrase III (CAIII) based on the amino acid sequence of a peptide obtained on lysyl endopeptidase digestion. CAIII is expressed as one of the major Zn-binding proteins in the livers of male rats in an age-dependent manner, a comparable amount of Zn to that of copper, Zn-superoxide dismutase (Cu,Zn-SOD) being bound to CAIII at 8 weeks of age. Castration at 4 or 8 weeks of age was shown to reduce Zn bound to CAIII to 47.5% of the sham-operated control level, suggesting that the sex-dependent expression of CAIII is partly regulated by a sex hormone, androgen. The concentration of CAIII in the livers of Long-Evans rats with a cinnamon-like coat color (LEC rats), an animal model of Wilson disease, was also estimated as Zn bound to CAIII and shown to be lower than that in Wistar rats before the onset of hepatitis. The concentration of CAIII was decreased specifically by repeated injections of cupric ions without the Cu,Zn-SOD concentration being affected.

Mechanism of hepatorenal syndrome in rats of Long-Evans Cinnamon strain, an animal model of fulminant Wilson's disease

Rats of Long-Evans Cinnamon (LEC) strain were used as a hepatorenal syndrome model of fulminant Wilson's disease. Copper levels in the kidneys increased markedly from 16 to 126 microg Cu/g from 12 to 16 weeks, and remained at the same level at 16 and 19 weeks when the rats suffered from severe renal dysfunction and also at 20 weeks in some other normal rats. The above findings imply that the renal dysfunction may have been induced independently of the copper level in the kidneys. The present study suggested the following mechanism: immediately after copper-induced hepatic dysfunction, plasma copper-metallothionein (CuMT), which was released from the liver, became elevated. The elevation was closely related to the increases in alkaline phosphatase, glucose and amino acids, all in the urine. The above findings suggest that plasma CuMT, which was released from the liver into the blood upon copper-induced hepatic dysfunction, was subsequently filtered at the glomeruli due to its smaller molecular weight, and then caused dysfunction of the brush border membrane of the renal proximal tubules probably after splitting into radical copper and amino acids in acidic vesicles close to the membrane. The critical concentration of plasma CuMT required to induce renal dysfunction was estimated as 1 microg Cu/l.

Association of copper to metallothionein in hepatic lysosomes of Long-Evans cinnamon (LEC) rats during the development of hepatitis [se e comments]

BACKGROUND

The Long-Evans cinnamon (LEC) rat has a mutation homologous to the human Wilson's disease gene, leading to copper-induced hepatotoxicity. The mechanism of how excess copper damages the liver or what chemical form of copper is toxic is still unclear.

RESULTS

In liver cytosol, copper levels were highest just before the onset of hepatitis and declined thereafter. In cytosol, total copper was bound to metallothionein (MT). Considerable amounts of both copper and iron accumulated in lysosomes with increasing age and development of liver damage. Lysosomal levels of presumably reactive non-MT-bound copper were increased. In severely affected livers, large amounts of copper were associated with insoluble material of high density which, upon ultrastructural information, was found to be derived from the lysosomes of Kupffer cells. This copper-rich material is considered to consist of polymeric degradation products of copper-MT.

CONCLUSION

We suggest that chronic copper toxicity in LEC rats involves the uptake of copper-loaded MT into lysosomes, where it is incompletely degraded and polymerizes to an insoluble material containing reactive copper. This copper, together with iron, initiates lysosomal lipid peroxidation, leading to hepatocyte necrosis. Subsequent to phagocytosis by Kupffer cells, the reactive copper may amplify liver damage either directly or through stimulation of these cells.

Biodistribution of [64Cu]Cu2+ and variance of metallothionein during tumor treatment by copper

The kinetic distribution patterns of [64Cu]Cu2+ in normal mice and in mice bearing tumors (HepA, ascitic tumor) after i.v. injection were similar. The i.v. injected [64Cu]Cu2+ concentrated into mouse liver first and then went to other organs and tissues, such as kidney and tumor. Most of the [64Cu]Cu2+ injected concentrated into the liver within 4 h, and about 8% of the total [64Cu]Cu2+ injected concentrated into the tumor cells at 24 h after i.v. injection. About 80% and 90% of the soluble [64Cu]Cu in the livers of tumor-bearing mice and normal mice, respectively, existed as [64Cu]CuMT (metallothionein [MT] is a small protein with many cysteine residues) at 4 h after i.v. injection, while about 43% of the soluble [64Cu]Cu2+ in tumor cells combined with MT at 6 h after i.v. injection. After 10 days oral administration of 150 microg/g body weight copper acetate, the concentration of MT in tumor cells reduced sharply, from 316 microg/g tissue to 152 microg/g tissue, while it increased slightly, from 375 microg/g tissue to 439 microg/g tissue, in the livers of tumor-bearing mice (HepA, solid tumor). The results suggest that MT contributes to the metabolism of copper that is localized mainly in the liver after copper administration and that copper can concentrate into mouse tumor cells followed by the reduction of MT in tumor cells.

Mechanisms of selective copper removal by tetrathiomolybdate from metallothionein in LEC rats

Copper (Cu) was selectively removed from metallothionein (MT) in the liver of LEC rats (Long-Evans rats with a cinnamon-like coat color) in vivo and in vitro by tetrathiomolybdate (TTM). Female LEC rats were injected intraperitoneally with TTM at a dose of 10 mg/kg body weight for 8 consecutive days. More than 2/3 of the Cu accumulating in the liver was removed by TTM treatment 24 h after the last injection. Although most Cu was bound to MT in the soluble fraction before TTM treatment, the Cu remaining in the liver was present almost exclusively in the non-soluble fraction together with molybdenum (Mo). Cu,Zn,Cd-MT was separated from the liver of LEC rats that had been injected with cadmium (Cd) and reacted with TTM at mol ratios of 0, 0.25, 0.50, 1.0, 2.0 and 4.0 to Cu bound to MT for 10 min at 37 degrees C. When TTM was added at a mol ratio of less than 1.0, a Cu,Zn,Cd-MT/TTM complex was detected, while addition of TTM at a mol ratio of greater than 1.0 selectively removed Cu from MT and produced a Cu/TTM complex via liberation of Zn,Cd-MT from the Cu,Zn,Cd-MT/TTM complex. Excessive TTM appeared to facilitate polymerization of the Cu/TTM complex to insoluble polymers. The dose-related formation of differing MT/TTM complexes explains the findings observed in vivo.

Systemic dispositions of molybdenum and copper after tetrathiomolybdate injection in LEC rats

Mutant Long-Evans rats with a cinnamon coat-color (LEC rats) have been established as an animal model for Wilson disease, a genetic disorder of copper (Cu) metabolism. Systemic disposition of molybdenum (Mo) and altered distributions of Cu were compared in eight organs between LEC rats and Wistar rats (normal) at different times after a single intraperitoneal injection of tetrathiomolybdate (TTM) for chelation therapy. Excretion through urine and feces was also examined. Hepatic disposition of Mo was dramatically increased in LEC rats, suggesting that the interaction of TTM with Cu results in enhanced uptake of Mo. Concentrations of Mo and Cu decreased in the liver of LEC rats over time, whereas those in the spleen increased. Although the concentration of Mo taken up by the kidney decreased over time after an initial increase in both rats, Cu concentration increased over time. Cu was not redistributed to the brain. Excretion of Mo through urine was decreased and that into feces was increased in LEC rats compared with those in Wistar rats. These results indicate that TTM is taken up by the liver depending on the Cu content, and the Cu and Mo removed from the liver are mostly excreted through feces. Redistribution of Cu was observed in the spleen and kidneys, but not in the brain.