Immunocytochemical identification of caeruloplasmin in hepatocytes of patients with Wilson's disease

A critical evaluation of copper metabolism in Indian Wilson's disease children with special reference to their phenotypes and relatives

Wilson's disease is an autosomal recessive disorder of copper accumulation in various organs, with most common clinical manifestations such as hepatic, neurological, and renal dysfunctions. Serum copper and ceruloplasmin in Wilson's disease were significantly lower as compared to normals, controls, and relatives of Wilson's disease patients, whereas marked hypercupriuria (145+/-7 microg/24 h) was observed in Wilson's children only. A good correlation (r=0.92) was found between non-ceruloplasmin-bound copper and 24-h urinary copper excretion in Wilson's disease patients. Further, copper studies among the different phenotypes of Wilson's disease revealed substantially low serum ceruloplasmin and a marked hypercupriuria in Wilson's disease children associated with renal tubular acidosis as compared to the patients with either hepatological or neurological manifestations. Serum ceruloplasmin levels in 14 patients of Wilson's disease were between 14 and 20 mg/dL. These patients of Wilson's disease were confirmed by measuring liver biopsy copper, which was about nine times higher than normal hepatic copper content. During the family screening by copper studies, four asymptomatic siblings were diagnosed for Wilson's disease. These subjects were then started on D-penicillamine therapy because presymptomatic treatment prevents progression of the disease complications.

Defective biliary copper excretion in Wilson's disease: the role of caeruloplasmin

Previous studies have failed to explain the link between copper accumulation and abnormal caeruloplasmin expression in Wilson's disease. Furthermore, despite the isolation of a candidate gene for Wilson's disease, which predicts a defective copper transport protein, the localization of this putative protein and its relationship to the pathway involved in copper excretion and to caeruloplasmin remain unknown. We now present evidence that caeruloplasmin, the major plasma copper-carrying protein, is present in the liver in Wilson's disease, and thus that reduced circulating levels of the protein result from a post-translational defect in the secretory pathway. We have also identified a novel form of caeruloplasmin, molecular weight 125 kD, which we propose may act as the carrier for excretory copper into bile, since it is normally present in both liver and bile, although largely absent from serum, and undetectable in bile from Wilson's disease patients. The presence of this form of caeruloplasmin in Wilson's disease liver suggests that a related post-translational defect may also be responsible for its absence from bile in Wilson's disease. This study thus provides the first plausible explanation of a link between the defective copper excretion and the reduced plasma caeruloplasmin, which characterize Wilson's disease.

Analysis of seven pedigrees of childhood Wilson's disease characterized by abdominal symptoms

In a survey of childhood Wilson's disease (WD) characterized by abdominal symptoms, three patients with high levels of immunologically detectable ceruloplasmin (CP) in serum were found. These three cases were compared with typical cases of WD in which serum CP level was low. In order to clarify the cause of WD, serum CP levels were quantified by two methods, an immunological protein assay and an oxidase activity assay. Using the results of these two assays, WD cases were classified into three groups on the basis of CP content; the first group consisted of patients with low enzyme activity and low CP protein content, the second group consisted of patients with low enzyme activity and normal CP protein content, and the third group, those patients with normal enzyme activity and normal CP protein content. No significant difference in symptoms was observed between these three groups. Since relatively high levels of CP were detected in some WD patients, genetic variation in CP in WD patients was examined by restriction enzyme fragment length polymorphism analysis using CP cDNA. However, no large deletion in the CP gene was detected. Using four types of gene probes for chromosome 13 known to be related to WD, the DNA of WD patients was examined in a similar fashion, but no significant difference was observed between the groups.

Molecular studies of ceruloplasmin deficiency in Wilson's disease

Deficiency of serum ceruloplasmin is a characteristic biochemical abnormality of Wilson's disease, although the mechanism of this finding is unknown. Ceruloplasmin messenger RNA (mRNA) levels were therefore examined in five patients with Wilson's disease and five controls with other types of hepatic disease. Northern and dot blot hybridizations showed that detectable ceruloplasmin mRNA was present in all of the patients with Wilson's disease, including one patient with no detectable serum ceruloplasmin. However, the ceruloplasmin mRNA levels in the Wilson's disease patients were only 33% that of controls (P less than 0.001). In contrast, albumin mRNA levels in the Wilson's disease patients averaged 161% that of controls. In an attempt to better delineate the level of gene expression responsible for this decrease in ceruloplasmin mRNA, the nuclear run-on assay was used to analyze transcriptional rates. The amount of ceruloplasmin gene transcription in four Wilson's patients was decreased to 44% that of three controls. These results indicate that the diminished serum ceruloplasmin levels in patients with Wilson's disease are due at least in part to a decrease in ceruloplasmin gene transcription.

The ontogeny of liver copper metabolism in the guinea pig: clues to the etiology of Wilson's disease

The normal human neonate has a copper profile indistinguishable from Wilson's disease, and we have previously postulated that this disease is caused by genetic failure to switch from the fetal to adult mode of copper metabolism. This study validates the developing guinea pig as a suitable animal in which to study copper ontogeny. At birth, liver copper concentrations are 7 times higher than in adults and serum copper and ceruloplasmin are 27 and 21% of adult values, respectively. A 53% fall in liver copper occurs in the 4 days after birth. This is associated with a marked increase in bile copper output, which does not parallel increasing bile flow. Liver copper falls, and serum copper and ceruloplasmin increase to near adult levels in the 30 days after birth. Until the sixtieth day of gestation, liver copper was significantly increased in copper-stressed littermates, although paradoxically at birth, concentrations were significantly lower. In copper-stressed fetal animals, bile copper output increased markedly before birth. Metallothionein was the dominant copper-binding protein in the fetal liver but a minor component in the adult. Superoxide dismutase activity only developed after birth. We conclude that the postnatal switch from the fetal to adult mode of copper metabolism involves activation of biliary excretion and ceruloplasmin export as well as changes in the association of copper with hepatic copper proteins. Similarities between the fetus and Wilson's disease suggest that this disease is caused by failure of this postnatal adaptation process.