Histochemical demonstration of copper in LEC rat liver

The interactions between iron and copper in genetic iron overload syndromes and primary copper toxicoses in Japan

Iron and copper are trace elements essential for health, and iron metabolism is tightly regulated by cuproproteins. Clarification of the interactions between iron and copper may provide a better understanding of the pathophysiology and treatment strategy for hemochromatosis, Wilson disease, and related disorders. The hepcidin/ferroportin system was used to classify genetic iron overload syndromes in Japan, and ceruloplasmin and ATP7B were introduced for subtyping Wilson disease into the severe hepatic and classical forms. Interactions between iron and copper were reviewed in these genetic diseases. Iron overload syndromes were classified into pre-hepatic iron loading anemia and aceruloplasminemia, hepatic hemochromatosis, and post-hepatic ferroportin disease. The ATP7B-classical form with hypoceruloplasminemia has primary hepatopathy and late extra-hepatic complications, while the severe hepatic form is free from ATP7B mutation and hypoceruloplasminemia, and silently progresses to liver failure. A large amount of iron and trace copper co-exist in hepatocellular dense bodies of all iron overload syndromes. Cuproprotein induction to stabilize excess iron should be differentiated from copper retention in Wilson disease. The classical form of Wilson disease associated with suppressed hepacidin25 secretion may be double-loaded with copper and iron, and transformed to an iron disease after long-term copper chelation. Iron disease may not be complicated with the severe hepatic form with normal ferroxidase activity. Hepatocellular dense bodies of iron overload syndromes may be loaded with a large amount of iron and trace copper, while the classical Wilson disease may be double-loaded with copper and iron.

Effects of N-Acetylcysteine, Quercetin, and Phytic Acid on Spontaneous Hepatic and Renal Lesions in LEC Rats

The effects of anti-oxidants were examined in Long-Evans Cinnamon (LEC) rats, which develop acute hepatic injury, and subsequent hepatic and renal tumors due to accumulation of excess Cu. The rats, at the age of 15 weeks, were supplied a diet containing either 1% of N-acetylcysteine (NAC), quercetin (QC), or phytic acid (PA), or basal diet alone. At weeks 2 and 6 posttreatment, animals were sacrificed for collection of blood and tissue samples. In the NAC-treated group, the development of hepatic and renal lesions was dramatically reduced. In addition, accumulation of Cu and Fe in the liver was suppressed. Acrolein-modified protein, a new marker for lipid peroxidation, was not detected in the liver or kidney of NAC treated rats, even though deposition was evident in control. Neither QC nor PA affected the development of spontaneous hepatic lesions. These results indicate that oxidative stress was reduced by NAC in the liver and kidney, and suggest that Cu and Fe may be involved in the generation of oxidative stress in the liver. In addition, it was suggested that the different effects of the anti-oxidants on lesion development in LEC rats might be related to different mechanisms of action with regard to oxidative stress.

Localization of the induced metallothionein and DNA damage in rat kidney after gold injection

To clarify the relationships between DNA damage and Cu-MT and between DNA damage and Cu in kidneys of rats injected with Au, we examined the histochemical localization of DNA damage, metallothionein (MT), and the accumulated Cu in the kidneys of rats injected with Au, Cu, or Cu-MT. The immunoreactivity of MT was observed predominantly in the outer stripe of the outer medulla and the inner cortex of the Au-injected rat, and the signals of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) were observed in the cortex. Cu detected by Timm's method was mainly distributed in the cortex of the Au-injected rat. These results indicated that DNA damage could be caused by free Cu in the cortex but not by the Cu bound to MT in the outer stripe of the outer medulla. This consideration was supported by the data from rats injected with Cu and Cu-MT. Furthermore, we determined the Cu contents in three fractions (cytosol, organelle, and precipitate-containing nuclei) of the kidneys. Interestingly, most of the Cu content in the kidney of the rat injected with Au or Cu-MT was detected in the cytosol, whereas most of the Cu content in the kidney of the rat injected with Cu was detected in the nuclei-containing precipitate. These findings suggest that the DNA damage in the kidneys of rats injected with Au may be associated with Cu-binding proteins but not with Cu-MT.

Role of copper accumulation in spontaneous renal carcinogenesis in Long-Evans Cinnamon rats

Spontaneous renal cell tumors in totals of 223 male and female Long-Evans Cinnamon (LEC) rats of 51-120 weeks old, 157 male F344 rats of 51-120 weeks old, and 14 male Long-Evans Agouti (LEA) rats of 51-70 weeks old were examined histologically. The incidences of renal cell tumors increased with age in male and female LEC rats, but no tumors developed in F344 or LEA rats. Dilated atypical tubules of the kidneys were observed at high incidence in aged LEC rats. Copper staining of LEC rat kidneys showed a positive reaction in proximal tubules of the cortex and the outer stripe of the medulla. The renal copper concentration of LEC rats reached a peak in the period of necrotizing hepatitis with renal tubular necrosis, and was higher than that in F344 rats for up to 106 weeks. In contrast, the renal iron concentration of LEC rats was lower than that in F344 rats except in the period of necrotizing hepatitis. Long-term treatment of LEC rats with D-penicillamine, a copper-chelating agent, inhibited accumulation of copper, but not iron, in the kidneys, and inhibited the development of karyomegaly of proximal tubules and dilated atypical tubules. These results suggest that persistent copper accumulation after toxic necrosis of tubules is the major cause of spontaneous renal carcinogenesis in LEC rats.

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.

Value of histochemical stains for copper in the diagnosis of Wilson's disease

AIMS

The histochemical demonstration of hepatic copper is important in the diagnosis of Wilson's disease (WD). Conflicting results have been published with regard to the ability of different histochemical methods to demonstrate copper storage in the liver. Therefore, we evaluated the diagnostic value of three available histochemical methods in a large series of patients affected by WD.

METHODS AND RESULTS

Seventy-nine consecutive liver needle biopsies, from 74 patients, 39 males and 35 females, aged 4-60 years (mean age 28.5 years) were stained with orcein, rhodanine and using Timm's method. On the basis of the histological picture, liver biopsies were subdivided into three groups: group A, steatosis; group B, interface hepatitis; group C, chronic hepatitis with bridging fibrosis and/or cirrhosis. In group A, 30.4% of the cases were positive using Timm's method, vs 13.2% using the rhodanine and 17.5% using the orcein method. In group B, Timm's method was positive in 40.1% while rhodanine and orcein showed positivity in 26.7%. In group C, the Timm's method stained 58.6%, rhodanine 36.6% and orcein 29.3% positively.

CONCLUSIONS

Our data show that: (1) Timm's silver stain is the most sensitive method for the demonstration of copper in all cases of WD; (2) rhodanine and orcein have minor value in the diagnosis of WD, especially in the early stages of the disease; (3) to increase the diagnostic value of histochemistry for copper multiple histochemical stains in serial sections are required; and (4) although hepatic copper concentration is highest in the early stages of WD, the histochemical demonstration fails in a large number of cases.

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.

Activation of serum response factor in the liver of Long-Evans Cinnamon (LEC) rat

We have studied the DNA binding activities of transcription factors in the liver of Long-Evans Cinnamon (LEC) rats, an animal model of Wilson's disease. Owing to a genetic defect, this strain of rats accumulates excessive copper in the liver and develops severe hepatitis and hepatocellular carcinoma. We found that the DNA binding activity of the serum response factor (SRF) was higher in the liver of LEC rats (approximately 2-fold) than in that of Wistar rats. There was a close correlation between the intensity of the activity and the concentrations of copper in the nuclear protein. The DNA binding activity of Sp1, on the other hand, showed similar levels in both LEC and Wistar rats. SRF may play an important role in the development of hepatocellular carcinoma in LEC rats by mediating the proto-oncogene c-fos induction. We suggest that the copper in nuclear protein may be involved in the activation of SRF.

Localization of renal Cu-binding metallothionein induced by Au injection into rats

The localization of Au-induced metallothionein (MT) in kidneys is reported. Au, Cu and Zn contents in kidneys and liver increased after Au injection. Especially the Cu content in the kidney increased in comparison with the Zn content. The yellow-orange autofluorescent signals which are a marker of Cu-MT were observed predominantly in the outer stripe of the outer medulla with a ring shape in the kidneys of Au-injected rats. MT mRNA was also located in only the outer stripe of the outer medulla. Neither autofluorescence nor MT mRNA was found in the kidneys of control rats. These results indicate that MT was biosynthesized in only the outer stripe of the outer medulla and the biosynthesized MT was bound to Cu. Representative Sephadex G-75 elution profiles of the renal cytosol of rats injected with Au showed that Au, Cu and Zn contents in MT fractions increased after Au injection. Interestingly, Cu in MT fractions dramatically increased in comparison with Zn in the MT fractions in spite of Au injection into rats. Only the Cu-containing MT fractions emitted a yellow-orange autofluorescence. The accumulated Cu in the kidneys of Au-injected rat was thought to be associated with renal toxicity.

Influence of copper on MRI of hepatocellular carcinoma

The purpose of this paper is to clarify whether copper accumulation in hepatocellular carcinoma (HCC) is a cause of high intensity signal pattern on T1-weighted images (T1-WI) by comparing the histologically proven copper accumulation with MR images. Forty-five surgically resected HCCs were analyzed. Distribution patterns of divalent copper by a modified Timm's method on their maximum cut surfaces were compared with signal patterns on corresponding T1-WI. The degree of copper accumulation in tumor compared with surrounding liver tissue was higher in 6 lesions, equal in 17 lesions, and lower in 22 lesions. High intensity pattern on T1-WI were observed in 3 of 6 lesions (50%), 10 of 17 lesions (59%), and 10 of 22 lesions (45%). Distribution patterns of copper were not correlated with intensity patterns on T1-WI. We conclude that the paramagnetic effect of divalent copper accumulation in HCC is insufficient to influence the MRI.

Copper and iron-induced oxidative damage in non-tumor bearing LEC rats

The copper and iron status in the liver of non-tumor bearing Long-Evans Cinnamon (LEC) rats (average age 17 months) was investigated. A direct quantitation of loosely-bound copper and iron was also investigated by using a chelating agent, nitrilotriacetic acid (NTA-chelatable free copper and iron). Besides the total copper and iron contents, the level of NTA-chelatable free copper was also higher in LEC rats than in LEA rats (P<0.05). But for the free iron level there was no significant difference between the two rat groups (P>0.05). The formation of thiobarbituric acid-reactive substances was higher in LEC rats than in LEA rats (P<0.01). The 4-hydroxy-2-nonenal (HNE)-modified proteins were also clearly demonstrated in LEC rat liver. The copper and iron which produced the most important effect in the process of oxidative damage in LEC rats could not be distinguished. Even though free copper, which could induce free radical injuries, was increased in LEC rats, neither tumor-induction nor preneoplastic lesions in the experimental LEC rats were observed. Therefore it is speculated that the elevation of a free iron is another important factor. Copper and iron, both important transition metals in the body, may participate in the induction of DNA damage and oncogenesis.

Melanin production by a filamentous soil fungus in response to copper and localization of copper sulfide by sulfide-silver staining

Gaeumannomyces graminis var. graminis, a filamentous soil ascomycete, exhibited enhanced cell wall melanin accumulation when exposed to as little as 0.01 mM CuSO(inf4) in minimal broth culture. Because its synthesis was inhibited by tricyclazole, the melanin produced in response to copper was dihydroxynaphthalene melanin. An additional hyphal cell wall layer was visualized by electron microscopy when hyphae were grown in the presence of copper and fixed by cryotechniques. This electron-dense layer was between the outer cell wall and the inner chitin layer and doubled the total wall thickness. In copper-grown cells that were also treated with tricyclazole, this electron-dense layer was absent. Atomic absorption spectroscopy demonstrated that up to 3.5 mg of Cu per g of fungal mycelium was adsorbed or taken up by hyphae grown in 0.06 mM CuSO(inf4). A method for silver enhancement was developed to determine the cellular location of CuS. CuS was present in cell walls and septa of copper-grown hyphae. Electron microscopy of silver-stained cells suggested that CuS was associated with the melanin layer of cell walls.

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).

The WD gene for Wilson's disease links to the hepatitis of LEC rats

LEC rats develop an autosomal recessive hepatitis and subsequently liver cancer associated with copper accumulation in the liver similar to that of Wilson's disease. Using 71 backcross [(WKAH x LEC) x LEC] rats, linkage analysis of the hepatitis with the WD gene for Wilson's disease revealed identical segregation and no recombination event between these two genes. This result indicates that the WD gene is a prime candidate for the hts gene responsible for the hepatitis of LEC rats, and suggests that the hepatitis of LEC rats may be caused by a defect in a copper-transporting ATPase expressed in the liver.