Expression of the Wilson disease gene is deficient in the Long-Evans Cinnamon rat

Inflammation-Related Carcinogenesis: Lessons from Animal Models to Clinical Aspects

Simple Summary

In multicellular organisms, inflammation is the body’s most primitive and essential protective response against any external agent. Inflammation, however, not only causes various modern diseases such as cardiovascular disorders, neurological disorders, autoimmune diseases, metabolic syndrome, infectious diseases, and cancer but also shortens the healthy life expectancy. This review focuses on the onset of carcinogenesis due to chronic inflammation caused by pathogen infections and inhalation/ingestion of foreign substances. This study summarizes animal models associated with inflammation-related carcinogenesis by organ. By determining factors common to inflammatory carcinogenesis models, we examined strategies for the prevention and treatment of inflammatory carcinogenesis in humans.

Abstract

Inflammation-related carcinogenesis has long been known as one of the carcinogenesis patterns in humans. Common carcinogenic factors are inflammation caused by infection with pathogens or the uptake of foreign substances from the environment into the body. Inflammation-related carcinogenesis as a cause for cancer-related death worldwide accounts for approximately 20%, and the incidence varies widely by continent, country, and even region of the country and can be affected by economic status or development. Many novel approaches are currently available concerning the development of animal models to elucidate inflammation-related carcinogenesis. By learning from the oldest to the latest animal models for each organ, we sought to uncover the essential common causes of inflammation-related carcinogenesis. This review confirmed that a common etiology of organ-specific animal models that mimic human inflammation-related carcinogenesis is prolonged exudation of inflammatory cells. Genotoxicity or epigenetic modifications by inflammatory cells resulted in gene mutations or altered gene expression, respectively. Inflammatory cytokines/growth factors released from inflammatory cells promote cell proliferation and repair tissue injury, and inflammation serves as a “carcinogenic niche”, because these fundamental biological events are common to all types of carcinogenesis, not just inflammation-related carcinogenesis. Since clinical strategies are needed to prevent carcinogenesis, we propose the therapeutic apheresis of inflammatory cells as a means of eliminating fundamental cause of inflammation-related carcinogenesis.

Simultaneous monitoring of cerebral metal accumulation in an experimental model of Wilson's disease by laser ablation inductively coupled plasma mass spectrometry

BACKGROUND

Neuropsychiatric affection involving extrapyramidal symptoms is a frequent component of Wilson's disease (WD). WD is caused by a genetic defect of the copper (Cu) efflux pump ATPase7B. Mouse strains with natural or engineered transgenic defects of the Atp7b gene have served as model of WD. These show a gradual accumulation and concentration of Cu in liver, kidneys, and brain. However, still little is known about the regional distribution of Cu inside the brain, its influence on other metals and subsequent pathophysiological mechanisms. We have applied laser ablation inductively coupled plasma mass spectrometry and performed comparative metal bio-imaging in brain sections of wild type and Atp7b null mice in the age range of 11-24 months. Messenger RNA and protein expression of a panel of inflammatory markers were assessed using RT-PCR and Western blots of brain homogenates.

RESULTS

We could confirm Cu accumulation in brain parenchyma by a factor of two in WD (5.5 μg g(-1) in the cortex) vs. controls (2.7 μg g(-1)) that was already fully established at 11 months. In the periventricular regions (PVR) known as structures of prominent Cu content, Cu was reduced in turn by a factor of 3. This corroborates the view of the PVR as efflux compartments with active transport of Cu into the cerebrospinal fluid. Furthermore, the gradient of Cu increasing downstream the PVR was relieved. Otherwise the architecture of Cu distribution was essentially maintained. Zinc (Zn) was increased by up to 40% especially in regions of high Cu but not in typical Zn accumulator regions, a side effect due to the fact that Zn is to some degree a substrate of Cu-ATPases. The concentrations of iron (Fe) and manganese (Mn) were constant throughout all regions assessed. Inflammatory markers TNF-α, TIMP-1 and the capillary proliferation marker α-SMA were increased by a factor of 2-3 in WD.

CONCLUSIONS

This study confirmed stable cerebral Cu accumulation in parenchyma and discovered reduced Cu in cerebrospinal fluid in Atp7b null mice underlining the diagnostic value of micro-local analytical techniques.

A novel rat model of hereditary hemochromatosis due to a mutation in transferrin receptor 2

Sporadic iron overload in rats has been reported, but whether it is due to genetic or environmental causes is unknown. In the current study, phenotypic analysis of Hsd:HHCL Wistar rats revealed a low incidence of histologically detected liver iron overload. Here we characterized the pathophysiology of the iron overload and showed that the phenotype is heritable and due to a mutation in a single gene. We identified a single male rat among the 132 screened animals that exhibited predominantly periportal, hepatocellular iron accumulation. This rat expressed low RNA levels of the iron regulatory hormone hepcidin and low protein levels of transferrin receptor 2 (Tfr2), a membrane protein essential for hepcidin expression in humans and mice and mutated in forms of hereditary hemochromatosis. Sequencing of Tfr2 in the iron-overloaded rat revealed a novel Ala679Gly polymorphism in a highly conserved residue. Quantitative trait locus mapping indicated that this polymorphism correlated strongly with serum iron and transferrin saturations in male rats. Expression of the Gly679 variant in tissue culture cell lines revealed decreased steady-state levels of Tfr2. Characterization of iron metabolism in the progeny of polymorphic rats suggested that homozygosity for the Ala679Gly allele leads to a hemochromatosis phenotype. However, we currently cannot exclude the possibility that a polymorphism or mutation in the noncoding region of Tfr2 contributes to the iron-overload phenotype. Hsd:HHCL rats are the first genetic rat model of hereditary hemochromatosis and may prove useful for understanding the molecular mechanisms underlying the regulation of iron metabolism.

The multi-layered regulation of copper translocating P-type ATPases

The copper-translocating Menkes (ATP7A, MNK protein) and Wilson (ATP7B, WND protein) P-type ATPases are pivotal for copper (Cu) homeostasis, functioning in the biosynthetic incorporation of Cu into copper-dependent enzymes of the secretory pathway, Cu detoxification via Cu efflux, and specialized roles such as systemic Cu absorption (MNK) and Cu excretion (WND). Essential to these functions is their Cu and hormone-responsive distribution between the trans-Golgi network (TGN) and exocytic vesicles located at or proximal to the apical (WND) or basolateral (MNK) cell surface. Intriguingly, MNK and WND Cu-ATPases expressed in the same tissues perform distinct yet complementary roles. While intramolecular differences may specify their distinct roles, cellular signaling components are predicted to be critical for both differences and synergy between these enzymes. This review focuses on these mechanisms, including the cell signaling pathways that influence trafficking and bi-functionality of Cu-ATPases. Phosphorylation events are hypothesized to play a central role in Cu homeostasis, promoting multi-layered regulation and cross-talk between cuproenzymes and Cu-independent mechanisms.

Molecular pathogenesis of Wilson and Menkes disease: correlation of mutations with molecular defects and disease phenotypes

The trace metal copper is essential for a variety of biological processes, but extremely toxic when present in excessive amounts. Therefore, concentrations of this metal in the body are kept under tight control. Central regulators of cellular copper metabolism are the copper-transporting P-type ATPases ATP7A and ATP7B. Mutations in ATP7A or ATP7B disrupt the homeostatic copper balance, resulting in copper deficiency (Menkes disease) or copper overload (Wilson disease), respectively. ATP7A and ATP7B exert their functions in copper transport through a variety of interdependent mechanisms and regulatory events, including their catalytic ATPase activity, copper-induced trafficking, post-translational modifications and protein-protein interactions. This paper reviews the extensive efforts that have been undertaken over the past few years to dissect and characterise these mechanisms, and how these are affected in Menkes and Wilson disease. As both disorders are characterised by an extensive clinical heterogeneity, we will discus how the underlying genetic defects correlate with the molecular functions of ATP7A and ATP7B and with the clinical expression of these disorders.

Copper and human health: biochemistry, genetics, and strategies for modeling dose-response relationships

Copper (Cu) and its alloys are used extensively in domestic and industrial applications. Cu is also an essential element in mammalian nutrition. Since both copper deficiency and copper excess produce adverse health effects, the dose-response curve is U-shaped, although the precise form has not yet been well characterized. Many animal and human studies were conducted on copper to provide a rich database from which data suitable for modeling the dose-response relationship for copper may be extracted. Possible dose-response modeling strategies are considered in this review, including those based on the benchmark dose and categorical regression. The usefulness of biologically based dose-response modeling techniques in understanding copper toxicity was difficult to assess at this time since the mechanisms underlying copper-induced toxicity have yet to be fully elucidated. A dose-response modeling strategy for copper toxicity was proposed associated with both deficiency and excess. This modeling strategy was applied to multiple studies of copper-induced toxicity, standardized with respect to severity of adverse health outcomes and selected on the basis of criteria reflecting the quality and relevance of individual studies. The use of a comprehensive database on copper-induced toxicity is essential for dose-response modeling since there is insufficient information in any single study to adequately characterize copper dose-response relationships. The dose-response modeling strategy envisioned here is designed to determine whether the existing toxicity data for copper excess or deficiency may be effectively utilized in defining the limits of the homeostatic range in humans and other species. By considering alternative techniques for determining a point of departure and low-dose extrapolation (including categorical regression, the benchmark dose, and identification of observed no-effect levels) this strategy will identify which techniques are most suitable for this purpose. This analysis also serves to identify areas in which additional data are needed to better define the characteristics of dose-response relationships for copper-induced toxicity in relation to excess or deficiency.

The LEC rat: a useful model for studying liver carcinogenesis related to oxidative stress and inflammation

Growing evidence indicates oxidative stress as a mechanism of several diseases including cancer. Oxidative stress can be defined as the imbalance between cellular oxidant species production and antioxidant capability shifted towards the former. Lipid peroxidation is one of the processes that takes place during oxidative stress. Lipid peroxidation products, such as malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), are closely related to carcinogenesis as they are potent mutagens and they have been suggested as modulators of signal pathways related to proliferation and apoptosis, two processes implicated in cancer development. Mechanisms by which oxidative stress leads to tumor formation are still under investigation. The need of suitable in vivo models that could reflect that inflammation-related human carcinogenesis is evident. In this regard, the mutant strain Long Evans Cinnamon-like (LEC) rat provides a promising model for investigation of the relationship between hepatitis induced by oxidative stress and hepatocarcinogenesis because it has been demonstrated to develop spontaneous liver tumor formation related to copper accumulation and oxidative stress. In this review, the findings regarding oxidative stress and its relation with liver pathologies in LEC rats are discussed; we focus on the mechanisms proposed for HNE carcinogenesis.

Copper transporters regulate the cellular pharmacology and sensitivity to Pt drugs

Recent studies have demonstrated that the major Cu influx transporter CTR1 regulates tumor cell uptake of cisplatin (DDP), carboplatin (CBDCA) and oxaliplatin (L-OHP), and that the two Cu efflux transporters ATP7A and ATP7B regulate the efflux of these drugs. Evidence for the concept that these platinum (Pt) drugs enter cells and are distributed to various subcellular compartments via transporters that have evolved to manage Cu homeostasis includes the demonstration of: (1) bidirectional cross-resistance between cells selected for resistance to either the Pt drugs or Cu; (2) parallel changes in the transport of Pt and Cu drugs in resistant cells; (3) altered cytotoxic sensitivity and Pt drug accumulation in cells transfected with Cu transporters; and (4) altered expression of Cu transporters in Pt drug-resistant tumors. Appreciation of the role of the Cu transporters in the development of resistance to DDP, CBDCA, and L-OHP offers novel insights into strategies for preventing or reversing resistance to this very important family of anticancer drugs.

Fe(II)/Cu(I)-dependent P-type ATPase activity in the liver of long-evans cinnamon rats

This study examined Fe(II)-dependent ATPase activity in OTG (octylthioglucoside) -treated microsomes isolated from Wistar and LEC rats. The ATPase activity of the liver OTG-microsomes from Wistar rats increased sharply in the 5-150 microM range of Fe(II) with a K0.5 value of 23.9+/-3.6 microM, while the activity of LEC rat liver microsomes increased with increasing Fe(II) up to 500 microM with a K0.5 value of 64.4+/-8.1 microM. The K0.5 values for Fe(II)-dependent ATPase activity of spleen OTG-microsomes were nearly identical at 59.3 microM in the Wistar rat and 63.7 microM in the LEC rats with a similar level of activity at each Fe(II) concentration in both strains of animals. These results indicated that there are two types of Fe(II)-dependent ATPase with different Fe(II) sensitivity, a high sensitive (H) and a low sensitive (L) type, and that the H-type activity was specific to the liver. The H-type activity was, however, deficient in the liver of LEC rats that accumulate copper and iron in hepatocytes as a result of mutations in the Wilson's disease protein (WNDP). On the basis of these results, together with the similarity in optimal conditions required for full activity of the enzyme, we conclude that the Fe(II)-dependent ATPase (H-type) and WNDP may be identical.

Value of an enzymatic assay for the determination of serum ceruloplasmin

The serum concentration of the copper protein ceruloplasmin has been an important diagnostic indicator of Wilson's disease (WD). It is widely quoted that 95% of people with WD have low serum ceruloplasmin concentrations. Current evidence suggests that a normal serum ceruloplasmin concentration is more common in patients with WD, particularly those with liver disease, perhaps in part because of the routine use of an immunologic assay. This assay might indicate a normal level of ceruloplasmin when the enzymatic activity is lower. Enzymatic activity is the biologically relevant parameter. We compared the immunologic measurement with the enzymatic assessment of oxidase activity in patients with liver or neurologic symptoms of unknown origin in whom WD was considered in the differential diagnosis. Although a strong correlation of ceruloplasmin protein concentration with oxidase activity was observed in controls, this was not the case for these patients. Twelve patients, presenting with various types of hepatic disease, demonstrated a weak correlation between ceruloplasmin protein concentration and oxidase activity. Ten percent of patients with neurologic symptoms ( n = 41) had low ceruloplasmin concentrations and oxidase activity, and another 8% had normal ceruloplasmin concentrations associated with low oxidase activity. Although the enzymatic method is preferred for its biologic relevance, ceruloplasmin analysis is not a reliable diagnostic parameter for the diagnosis of WD in patients with liver disease. An important use of the ceruloplasmin oxidase assay is in the follow-up of patients with WD. Ceruloplasmin oxidase activity was undetectable in sera from patients with WD who were undergoing long-term chelation therapy, suggesting an early sign of copper depletion and a need for subsequent monitoring for symptoms of copper deficiency.

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.

Implication of the differential roles of metallothionein 1 and 2 isoforms in the liver of rats as determined by polyacrylamide-coated capillary zone electrophoresis

Metallothioneins (MTs), determined by polyacrylamide-coated capillary zone electrophoresis (CZE), coincided well with those described by enzyme-linked immunosorbent assay. By using CZE, MT isoforms 1 (MT-1) and 2 (MT-2) were well separated and determined in the liver cytosol of LEC rats and Wistar rats administered CdCl(2). The total concentrations of MTs in the liver cytosol of LEC rats increased age-dependently as 1.0, 2.1, and 7.2mg/g wet weight of the liver at the age of 5, 10, and 15 weeks, respectively, and those of Wistar rats that had received daily CdCl(2) also increased with time of CdCl(2) as 0.5 and 1.2mg/g wet weight of the liver for 3 and 6 consecutive administration days, respectively. The MT-1/MT-2 ratio in the liver cytosol of LEC rats decreased age-dependently as 1.75, 1.49, and 0.76 at the age of 5, 10, and 15 weeks, respectively. In contrast, that of Wistar rats increased with time of exposure to the metal ion CdCl(2) as 1.1 and 1.6 for 3 and 6 administration days, respectively. Copper accumulation in the liver of LEC rats has already been reported. The present results indicated that the mechanism of the induction of MT synthesis differs between LEC rats, who lack ATP7B, and Wistar rats, who were given a toxic metal ion. On the basis of these results, we propose that MT-1 is related to the metabolism or detoxification of toxic metals such as Cd, and in contrast, MT-2 is responsible for the homeostasis of essential metals such as Cu.

Tetrathiomolybdate in the treatment of acute hepatitis in an animal model for Wilson disease

BACKGROUND/AIMS

Tetrathiomolybdate (TTM) is a potent copper-chelating agent that has been shown to be effective in Wilson disease patients with neurological symptoms. Here, we investigate the potential use of TTM in treating the acute hepatic copper toxicosis in Long-Evans Cinnamon (LEC) rats, an authentic model for Wilson disease.

METHODS

After the onset of acute hepatitis, LEC rats were treated once with 10 mg TTM/kg. After 1 and 4 days, parameters of liver toxicity and the subcellular distribution and binding of copper and iron were studied.

RESULTS

In 11 out of 12 rats TTM rapidly improved acute hepatitis. Hepatic copper decreased through removal from cytosolic metallothionein and lysosomal metallothionein polymers. The remaining lysosomal copper forms a metallothionein-copper-TTM complex. In an almost moribund rat, however, TTM caused severe hepatotoxicity with fatal outcome.

CONCLUSIONS

TTM is effective in treating acute hepatitis in LEC rats when applied before the animals become moribund. TTM appears to act by removing the presumable reactive copper associated to lysosomal metallothionein polymers. The remaining lysosomal copper seems to be inactivated by forming a complex with TTM. Moreover, TTM removes copper from cytosolic copper-containing metallothionein. As a consequence, metallothionein is degraded and the uptake of copper-metallothionein into the lysosomes and the formation of the metallothionein polymer associated copper is reduced.

Comparison of the Disposition Behavior of Organic anions in an Animal Model for Wilson's Disease (Long-Evans Cinnamon rats) with that in Normal Long-Evans Agouti rats

Long-Evans Cinnamon (LEC) rats have an abnormality similar to that observed in Wilson's disease in humans and are therefore a good animal model for the study of Wilson's disease. LEC rats develop hereditary hepatitis and severe jaundice. Mutant animals with hyperbilirubinemia have been widely used as animal models for human diseases. Among these mutant animals, Eisai hyperbilirubinemic rats (EHBR) have defective biliary excretion of organic anions. Thus, biliary excretion of sulfobromophthalein (BSP) and urinary excretion of phenolsulfonphthalein (PSP) in LEC rats were compared with those in Long-Evans Agouti (LEA) rats. In LEC rats, the excretion of BSP, a multidrug resistance-associated protein 2 (Mrp2/Abcc2) substrate, was significantly decreased compared to that in LEA rats. It has been reported that the transport function for organic anions on the kidney is maintained in EHBR. However, the urinary excretion of PSP is impaired in LEC rats. It is possible that organic anion transporters responsible for the urinary excretion of PSP in LEA rats and EHBR are impaired in LEC rats. It is important to elucidate the relationship between organic anion secretion and Wilson's disease.

Copper in disorders with neurological symptoms: Alzheimer's, Menkes, and Wilson diseases

Copper is an essential element for the activity of a number of physiologically important enzymes. Enzyme-related malfunctions may contribute to severe neurological symptoms and neurological diseases: copper is a component of cytochrome c oxidase, which catalyzes the reduction of oxygen to water, the essential step in cellular respiration. Copper is a cofactor of Cu/Zn-superoxide-dismutase which plays a key role in the cellular response to oxidative stress by scavenging reactive oxygen species. Furthermore, copper is a constituent of dopamine-beta-hydroxylase, a critical enzyme in the catecholamine biosynthetic pathway. A detailed exploration of the biological importance and functional properties of proteins associated with neurological symptoms will have an important impact on understanding disease mechanisms and may accelerate development and testing of new therapeutic approaches. Copper binding proteins play important roles in the establishment and maintenance of metal-ion homeostasis, in deficiency disorders with neurological symptoms (Menkes disease, Wilson disease) and in neurodegenerative diseases (Alzheimer's disease). The Menkes and Wilson proteins have been characterized as copper transporters and the amyloid precursor protein (APP) of Alzheimer's disease has been proposed to work as a Cu(II) and/or Zn(II) transporter. Experimental, clinical and epidemiological observations in neurodegenerative disorders like Alzheimer's disease and in the genetically inherited copper-dependent disorders Menkes and Wilson disease are summarized. This could provide a rationale for a link between severely dysregulated metal-ion homeostasis and the selective neuronal pathology.

ACP Best Practice No 163. Wilson's disease: acute and presymptomatic laboratory diagnosis and monitoring

Wilson's disease, the most common inherited disorder of copper metabolism, is a recessive genetic condition. The clinical presentation of Wilson's disease is very variable. It is characterised by low serum copper and caeruloplasmin concentrations coupled with the pathological accumulation of copper in the tissues. However, there are diagnostic difficulties and these are discussed. The current value of DNA diagnosis, both in gene tracking in families or as applied to de novo cases, is examined. Wilson's disease can be treated successfully but treatment must be life long. Patients are best treated by specialist centres with experience and expertise in the condition.

Spontaneous porphyria of the Long-evans cinnamon rat: an animal model of Wilson's disease

To confirm and extend our previous microspectrophotometric observations of 30-week-old male Long-Evans Cinnamon (LEC) rats, an animal model of human Wilson's disease, we analyzed the porphyrin patterns of the organs, urine, and plasma of LEC rats. Abnormal accumulation of porphyrins, especially highly carboxylated porphyrins (uro- and heptaporphyrin), in the kidneys and liver was seen in male and female LEC rats aged 30 weeks and also in 10-week-old rats, before the onset of spontaneous hepatic dysfunction. Accumulation of copper and iron in the kidneys was not observed in the 10-week-old rats. Massive accumulation of porphyrins was observed only in the kidneys of the 30-week-old male LEC rat, indicating that this symptom is related to sex and age. Renal accumulation of porphyrins was reflected in the rate of urinary porphyrin excretion. Hepatic accumulation of porphyrins appeared to be independent of sex and age. These results indicate that neither renal nor hepatic porphyrin accumulation is the result of renal deposition of metals or of spontaneous hepatic dysfunction and that porphyrinuria in the LEC rat is closely related to the renal accumulation of porphyrins. In contrast to these organs, a reduction in the porphyrin levels was observed in the brain of the LEC rat. This was independent of sex and age. The present work stresses the existence of an abnormal heme metabolism in the LEC rat, and thus, the necessity to study the heme metabolism in human Wilson's disease is strongly suggested.

The Long-Evans Cinnamon rat: an animal model for Wilson's disease

The Long-Evans Cinnamon (LEC) rat is known to develop hepatitis and liver cancer spontaneously, phenomena attributed to abnormal copper metabolism. This mutant strain of rat shows some clinical features that are similar to those of Wilson's disease, including excessive copper in the liver, reduced excretion of copper into bile, a reduced level of serum copper and a remarkable decrease in serum ceruloplasmin activity. Molecular studies have revealed that the copper transporting P-type ATPase, atp7b, which is the rat gene homologous to human ATP7B, was found to be defective in the LEC rat. These observations have confirmed that the LEC rat is a rodent model for Wilson's disease. In addition, recent studies have suggested that the ATP7B protein is involved in the intracellular transport of hepatic copper. The absence or diminution of ATP7B function results in abnormal copper metabolism in the LEC rat and in patients with Wilson's disease.

Wilson's disease: copper unfettered

Wilson's disease is a rare autosomal recessive inherited disorder of copper metabolism. Hepatic excretion of copper is impaired due to mutation of the gene for a copper-transporting adenosine triphosphatase, ATP7B. Copper accumulation in liver, brain, and other tissues may cause a wide spectrum of hepatic, neuropsychiatric, and other clinical manifestations. The diagnosis may be supported by measurement of serum ceruloplasmin, urinary copper excretion, and hepatic copper content as well as by detection of Kayser-Fleischer rings. Several treatments are available to increase urinary excretion and decrease intestinal absorption of copper.

Biliary excretion of copper in LEC rat after introduction of copper transporting P-type ATPase, ATP7B

Wilson's disease, an autosomal recessive disorder, is characterized by the excessive accumulation of hepatic copper that results from reduced biliary copper excretion and disturbed incorporation of copper into ceruloplasmin. The ATP7B gene, responsible for the disease, encodes a copper transporting P-type ATPase. We previously demonstrated the involvement of ATP7B in hepatic copper secretion into plasma after the introduction of ATP7B into the Long-Evans Cinnamon (LEC) rat, a rodent model of Wilson's disease. In this study we found the increased copper contents of the hepatic lysosomal fractions and bile in the LEC rats after ATP7B introduction, indicating the participation of ATP7B in the biliary excretory pathway for copper.

Hepatocyte-specific localization and copper-dependent trafficking of the Wilson's disease protein in the liver

Wilson's disease is an inherited disorder of copper metabolism characterized by hepatic cirrhosis and neuronal degeneration. In this current study, a polyclonal antiserum specific for the Wilson's disease ATPase was used to examine the hepatic expression of this protein. Immunoblot analysis of lysates from human and rat liver detected a single 165-kDa protein, which by immunofluorescence was present only in hepatocytes and localized predominantly to the trans-Golgi network and exclusively in this compartment under low hepatic copper concentrations. Although hepatic copper concentration had no effect on the steady-state levels of the Wilson's disease protein, copper administration in vivo resulted in redistribution of this protein to a cytoplasmic vesicular compartment localized toward the hepatocyte canalicular membrane. The relative abundance of the Wilson's disease protein in the liver was found to be greatest in the fetus before the onset of biliary copper excretion. Taken together, these studies reveal a novel posttranslational mechanism of copper homeostasis in vivo consistent with the proposed function of the Wilson's disease protein in holoceruloplasmin biosynthesis and biliary copper excretion and of relevance to the broad clinical heterogeneity observed in this disease.

Characterization of a heavy metal ion transporter in the lysosomal membrane

Lysosomes are thought to play a role in various aspects of heavy metal metabolism. In the present study we demonstrate for the first time the presence of a heavy metal ion transport protein in the lysosomal membrane. Uptake of radioactive silver both in highly purified lysosomal membrane vesicles and in purified intact lysosomes showed the typical kinetics of a carrier-mediated process. This transport was stimulated by ATP hydrolysis, and showed specificity for Ag+, Cu2+, and Cd2+. All biochemical properties of this lysosomal metal ion transporter could classify it as a heavy metal transporting P-type ATPase. Long Evans Cinnamon (LEC) rats, an animal model for the copper transport disorder Wilson disease, showed normal lysosomal silver transport.

Functional expression of the Wilson disease protein reveals mislocalization and impaired copper-dependent trafficking of the common H1069Q mutation

Wilson disease is an autosomal recessive disorder of hepatic copper metabolism caused by mutations in a gene encoding a copper-transporting P-type ATPase. To elucidate the function of the Wilson protein, wild-type and mutant Wilson cDNAs were expressed in a Menkes copper transporter-deficient mottled fibroblast cell line defective in copper export. Expression of the wild-type cDNA demonstrated trans-Golgi network localization and copper-dependent trafficking of the Wilson protein identical to previous observations for the endogenously expressed protein in hepatocytes. Furthermore, expression of the Wilson cDNA rescued the mottled phenotype as evidenced by a reduction in copper accumulation and restoration of cell viability. In contrast, expression of an H1069Q mutant Wilson cDNA did not rescue the mottled phenotype, and immunofluorescence studies showed that this mutant Wilson protein was localized in the endoplasmic reticulum. Consistent with these findings, pulse-chase analysis demonstrated a 5-fold decrease in the half-life of the H1069Q mutant as compared with the wild-type protein. Maintenance of these transfected cell lines at 28 degreesC resulted in localization of the H1069Q protein in the trans-Golgi network, suggesting that a temperature-sensitive defect in protein folding followed by degradation constitutes the molecular basis of Wilson disease in patients harboring the H1069Q mutation. Taken together, these studies describe a tractable expression system for elucidating the function and localization of the copper-transporting ATPases in mammalian cells and provide compelling evidence that the Wilson protein can functionally substitute for the Menkes protein, supporting the concept that these proteins use common biochemical mechanisms to effect cellular copper homeostasis.

Wilson's disease. Update of a systemic disorder with protean manifestations

In Wilson's disease, a genetic defect in a copper transporter causes defective incorporation of copper into apo-ceruloplasmin and the failure to excrete copper into bile. Copper accumulated in hepatocytes generates damage via reactive oxygen species. Release of copper from necrotic hepatocytes leads to damage of other tissues, including the brain, urinary tract, red blood cells, heart, endocrine glands, skin, pancreas, bones, and joints. Treatment is designed to chelate the excess copper for urinary excretion, prevent copper absorption, and render tissue copper nontoxic. Liver transplantation, with replacement of the defective hepatic gene, may be necessary in some cases.

Different pathomorphologic patterns in exogenic infantile copper intoxication of the liver

Pathomorphology of the liver has been reviewed in 12 German infants with chronic exogenic copper intoxication. In 8 cases severe liver damage with diffuse accumulation of Mallory bodies and liver cell necrosis mimicking florid Indian childhood cirrhosis (ICC) was found. Seven of these children died because of liver failure. One child received liver transplantation at the age of 9 months. In contrast, 4 children with a stable clinical course had a complete micronodular cirrhosis in liver biopsy. The characteristic morphological features of ICC, especially ballooning of liver cells and accumulation of Mallory bodies, were only slightly expressed or even lacking. There was no correlation between the copper content of the liver and the severity of liver damage. The copper concentration varied between 541 micrograms/g dry weight (norm < 50 micrograms/g) and 2.154 micrograms/g dry weight in fatal cases. In surviving infants even higher concentrations of up to 698 micrograms/g fresh weight (norm < 5 micrograms/g), were found. The amount of free cytosolic copper varied between 900-4,900 ng/mg protein (13-70 times of normal). In conclusion, a spectrum of pathomorphological alterations exists in exogenic infantile copper disease which correlates with the clinical outcome in contrast to the copper content of the liver. Copper intoxication of the liver should be of diagnostic concern in any case of unclear micronodular cirrhosis in early infancy.

A marked increase in free copper levels in the plasma and liver of LEC rats: an animal model for Wilson disease and liver cancer

Most of copper present in rat plasma and liver binds to caeruloplasmin and metallothionein, respectively, and is not redox active. However, free forms of copper including loosely bound forms to other molecules are redox active. We assessed the free copper in Long-Evans rats with a cinnamon-like coat color (LEC rats), an animal model of Wilson disease and liver cancer. Compared to those of control rats, the liver and plasma of LEC rats showed a marked elevation of free copper, especially at the stage of acute hepatitis, in parallel with an increase of total copper levels in the livers and a decrease of plasma caeruloplasmin (ferroxidase I) activity. At the onset of jaundice, the total copper levels, however, decreased in liver, but increased in plasma, while free copper levels in both liver and plasma remained higher. Free iron levels in both liver and plasma were also determined and did not change significantly, except for the case of plasma in jaundiced rats. The data are consistent with a proposal in which increased levels of redox active free copper in the liver of LEC rats catalyze Fenton-type reactions, producing a large flux of hydroxyl radicals that would play an important role in the observed liver dysfunction, leading to acute hepatitis, and finally, hepatocarcinoma. This is the first demonstration that the free copper may participate in the pathophysiology of the LEC rats and Wilson disease.

Targeting of tetrathiomolybdate on the copper accumulating in the liver of LEC rats

The uptake of tetrathiomolybdate (TTM) by the liver and the removal of copper (Cu) accumulating in the liver in a form bound to metallothionein (MT) by TTM were studied in Long-Evans cinnamon (LEC) rats, an animal model of Wilson disease, in order to develop better treatments for the disease and Cu toxicity. Although molybdenum (Mo) was incorporated in a dose-dependent manner into the livers of both LEC and Long-Evans agouti (LEA) rats, the original strain of LEC rats used as a reference animal, the uptake into the liver of LEC rats was 13 times higher than that in LEA rats. The concentration of Mo in the soluble fraction plateaued and it was distributed more in the insoluble fraction with a higher dose in LEC rats. The concentration of Cu in the whole livers of LEC rats was decreased by TTM in a dose-dependent manner only at lower doses. However, the concentration of Cu in the soluble fraction continued to decrease with the dose of TTM. The results can be explained in terms of complex formation. Namely, TTM forms a complex with Cu, tentatively referred to a Cu/TTM complex, that can be effluxed into the bloodstream, and then binds selectively to albumin when the dose of TTM is low. On the other hand, TTM forms an insoluble complex, named as a Cu/TTM polymer that is precipitated in the liver when the dose is high. The results further indicate that TTM taken up by a cell is immobilized in the cell through the dose-dependent formation of a complex containing Cu, Mo and sulfur (S), which causes further uptake of TTM. TTM injected into rats or incubated in vitro with serum does not remove Cu from ceruloplasmin. TTM is, thus, suggested to target a cell accumulating excess Cu as Cu-MT, and to remove Cu selectively without interacting with Cu in Cu-enzymes. The results indicate that TTM is taken up by the liver depending on the amount of Cu accumulating in the form of MT, and then Cu is effluxed together with Mo in the form of Cu/TTM complex into the bloodstream.

A high expression of heme oxygenase-1 in the liver of LEC rats at the stage of hepatoma: the possible implication of induction in uninvolved tissue

We have examined changes in the expression of heme oxygenase-1 (HO-1), an inducible isoform and HO-2, a constitutive isoform, in the liver of Long-Evans with a Cinnamon-like color (LEC) rat, a mutant strain which spontaneously develops acute hepatitis and hepatoma. HO-1 expression was highly enhanced in the LEC rat livers with jaundice, and then decreased slightly, but overall remained at a higher level than in the Long-Evans with Agouti color (LEA) control rats, as judged by Northern blotting analysis of the whole liver extract. The high expression of HO-1 in the LEC rat liver was, however, not due to the actual cancer lesion but, rather, due to the surrounding uninvolved tissues including hepatocytes. Immunohistochemical analysis also supported this conclusion. Among normal tissues, the expression of HO-1 but not HO-2 was high in only the spleen of both LEC and LEA rats. The high expression observed in the stage of acute hepatitis and hepatoma stages in the LEC rat is probably due to the oxidative stress caused by the accumulation of free copper and free iron levels which has been reported earlier by our group (Suzuki et al., Carcinogenesis, 1993, 14, 1881-1884 and Koizumi et al., Free Radical Research, in press) as well as by free heme levels. The inflammatory cytokines produced by the surrounding tissue at the hepatoma stage would also be expected to play a role in the induction mechanism. The physiological relevance of HO-1 induction might be an adaptive response to oxidative stress and vasodilatory effect of carbon monoxide on sinusoidal circulation.

The LEC rat possesses reduced hepatic selenium, contributing to the severity of spontaneous hepatitis and sensitivity to carcinogenesis

The hepatic concentrations of copper, zinc, magnesium, calcium, and selenium were measured in LEC rats, which develop a spontaneous form of hepatitis at 3-4 months of age, and compared to trace metal concentrations in the LEA rat, its asymptomatic congenic strain. Consistent with results found by other groups, copper was found to accumulate within the liver of LEC rats to levels more than 50 times those measured in LEA rats. In addition, liver selenium concentration in LEC rats was found to be around 50% of that in LEA rats. The enzyme activity, and RNA for the selenium dependent enzyme, glutathione peroxidase, was also found to be reduced in LEC rat liver. These results indicate that hepatic selenium in the LEC rat is depleted and that, as a result of this, the capacity to protect cells from copper-induced free-radical damage is reduced.

Restoration of holoceruloplasmin synthesis in LEC rat after infusion of recombinant adenovirus bearing WND cDNA

Wilson's disease, an autosomal recessive disorder, is characterized by the excessive accumulation of copper in the liver. WND (ATP7B) gene, which encodes a putative copper transporting P-type ATPase, is defective in the patients. To investigate the in vivo function of WND protein as well as its intracellular localization, WND cDNA was introduced to the Long-Evans Cinnamon rat, known as a rodent model for Wilson's disease, by recombinant adenovirus-mediated gene delivery. An immunofluorescent study and a subcellular fractionation study revealed the transgene expression in liver and its localization to the Golgi apparatus. Moreover, since the synthesis of holoceruloplasmin is disturbed in the Long-Evans Cinnamon rat, the plasma level of holoceruloplasmin, oxidase-active and copper-bound form, was examined to evaluate the function of WND protein with respect to the copper transport. Consequently, the appearance of holoceruloplasmin in plasma was confirmed by Western blot analysis and plasma measurements for the oxidase activity and the copper content. These findings indicate that introduced WND protein may function in the copper transport coupled with the synthesis of ceruloplasmin and that the Golgi apparatus is the likely site for WND protein to manifest its function.

Abnormal accumulation of porphyrin derivatives in the kidneys of Long-Evans Cinnamon rats, as evidenced by microspectrophotometry

In the study described here we have revealed an abnormal accumulation of porphyrin derivatives in the kidneys of Long-Evans Cinnamon (LEC) rats, an animal model for human Wilson's disease. In addition, we have confirmed that the derivatives emitted red-orange light in renal sections under UV excitation. This renal red-orange emission has previously been identified as luminescence from cuprous metallothioneins [Cu(I)-MTs], which also accumulate in both the kidneys and liver of LEC rats. In this study, we measured the emission spectra of the luminescence in the kidneys using microspectrophotometry. The spectra of the renal red-orange emission resembled those of porphyrin derivatives rather than those of Cu(I)-MTs. We then extracted these derivatives from the kidneys. An abundance of porphyrin derivatives was established. A significant increase in the levels of the derivatives in the liver and urine of the LEC rats was also confirmed. These results provide evidence of a heme-metabolism abnormality in LEC rats.

Accumulation of orally given cadmium in Long-Evans Cinnamon (LEC) rats with an inherently abnormal copper metabolism

An inherent defect of biliary Cu excretion and subsequent Cu deposition in the liver have been found in Long-Evans Cinnamon (LEC) rats, which are promising models of Wilson disease. LEC and Fischer rats were given water containing Cd (CdCl2) at a level of 5 ppm for 30 days. Regardless of drinking Cd water, LEC rats showed a very high concentration of Cu (200 to 250 microgram/g) and Cu-metallothionein (Cu-MT) (18 mg/g) in the liver. There was no difference of Cd accumulation in the liver between the two strains exposed to Cd (2.6 and 2.7 microgram/g in the Fischer and LEC groups, respectively). However, the renal Cd concentration was slightly but significantly higher in LEC rats (3.5 microgram/g) than in Fischer rats (2.0 microgram/g). The ratio of renal Cd contents to the sum of renal and hepatic Cd contents was significantly higher in LEC rats (0.25) than in Fischer rats (0.15). The serum Cd concentration in Cd-treated LEC rats increased threefold compared to Cd-treated Fischer rats. It seems likely that Cd from the liver is transported into the kidney in the form of Cd, Cu-MT. There was no difference in uptake of Cd in the hepatic MT fraction between the two strains. Although biliary Cu excretion in LEC rats was significantly lower than that in Fischer rats, reduced excretion of Cd into bile was not found in LEC rats. The gross amounts of Cu and Cu-MT influenced the accumulation of Cd in the kidney rather than in the liver when Cd was given orally at a low level to LEC rats. Our results suggest tht Cu and Cd do not share the same sites of hepatobiliary excretion in rats, although the main route of their excretion is via bile.

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.

Molybdenum and copper kinetics after tetrathiomolybdate injection in LEC rats: specific role of serum albumin

Chelation therapy with tetrathiomolybdate (TTM) was applied to Long-Evans rats with a cinnamon coat-color (LEC rats), an animal model for Wilson disease, to remove copper (Cu) accumulated in the liver in a form bound to metallothionein (MT). Changes in molybdenum (Mo) and Cu concentrations and their biological forms in serum of LEC rats determined at different times after a single intraperitoneal injection were compared with those of Wistar (normal) rats. The change in Mo concentration in serum of normal rats was mono-phasic, whereas in LEC rats it was bi-phasic. The phase in normal rats and the first phase in LEC rats appeared to reflect the process of uptake and disappearance of TTM in the livers of Wistar and LEC rats. On the other hand, the second phase in LEC rats paralleled the changes of Cu and appeared to reflect the complex formation (Cu/thiomolybdate complex) between Mo and Cu accumulated in the liver. The complex was specifically bound to albumin as determined by high performance liquid chromatography with inductively coupled plasma-mass spectrometry (HPLC/ICP-MS). The results suggested that the changes in the Mo concentration in serum reflected the amount of Cu in the liver.

Aceruloplasminemia: molecular characterization of this disorder of iron metabolism

Ceruloplasmin is an abundant alpha 2-serum glycoprotein that contains 95% of the copper found in the plasma of vertebrate species. We report here on the identification of a genetic defect in the ceruloplasmin gene in a patient previously noted to have a total absence of circulating serum ceruloplasmin in association with late-onset retinal and basal ganglia degeneration. In this patient T2 (transverse relaxation time)-weighted magnetic resonance imaging of the brain revealed basal ganglia densities consistent with iron deposition, and liver biopsy confirmed the presence of excess iron. Although Southern blot analysis of the patient's DNA was normal, PCR amplification of 18 of the 19 exons composing the human ceruloplasmin gene revealed a distinct size difference in exon 7. DNA sequence analysis of this exon revealed a 5-bp insertion at amino acid 410, resulting in a frame-shift mutation and a truncated open reading frame. The validity of this mutation was confirmed by analysis of DNA from the patient's daughter, which revealed heterozygosity for this same 5-bp insertion. The presence of this mutation in conjunction with the clinical and pathologic findings demonstrates an essential role for ceruloplasmin in human biology and identifies aceruloplasminemia as an autosomal recessive disorder of iron metabolism. These findings support previous studies that identified ceruloplasmin as a ferroxidase and are remarkably consistent with recent studies on the essential role of a homologous copper oxidase in iron metabolism in yeast. The clinical and laboratory findings suggest that additional patients with movement disorders and nonclassical Wilson disease should be examined for ceruloplasmin gene mutations.

Deletion of the Wilson's disease gene in hereditary hepatitis LEC rats

LEC rats develop disorder of cooper metabolism and hepatitis similar to those of human Wilson's disease. We recently demonstrated that the gene responsible for hepatitis (hts) of LEC rats is homologous to Wilson's disease gene (WD). The present study showed a deletion of at least 90 base pair of WD cDNA in LEC rats, which corresponds to nucleotides 3981 to 4071 in human WD cDNA sequence. This deletion was linked with hepatic copper accumulation and hepatitis, and considered to be a primary mutation for hepatic disorder in the LEC rat. The WD gene was assigned to rat chromosome 16 at band q12.2-q12.4 by fluorescence in situ hybridization (FISH).