Plasma copper, iron, ceruloplasmin and ferroxidase activity in schizophrenia

As ceruloplasmin and copper abnormalities have been implicated in schizophrenia, we investigated the role of a second copper-containing non-ceruloplasmin protein, the iron oxidase ferroxidase II, in a prospective study of ten inpatients with schizophrenia and a comparison group. Ferroxidase II is a protein known to reciprocally regulate with ceruloplasmin in Wilson's disease, an illness characterized by psychotic symptoms, decreased ceruloplasmin, and increased copper deposition in tissues. Ferroxidase II plays a key role in the maintenance of near-normal iron metabolism in Wilson's disease, but its role in schizophrenia has never been studied. In this study, we assayed ceruloplasmin by two enzymatic assays, a standard clinical laboratory p-phenylenediamine oxidation assay and a second assay based on the rate of the oxidation and incorporation of iron (Fe3+) into transferrin; we assayed ferroxidase II activity using this second iron oxidation assay. We found that ceruloplasmin levels as measured by both enzymatic methods, but not ferroxidase II, were elevated in schizophrenia. The increased ceruloplasmin also correlated with elevated serum copper as assayed by atomic absorption spectrophotometry, which was unsurprising as the majority of copper in blood is bound to ceruloplasmin. It has been proposed that copper, as a component of several enzymes linked to dopamine synthesis, may play a role in schizophrenia by exacerbating or perpetuating dopaminergic dysregulation. Our study suggests that the ceruloplasmin elevation in schizophrenia is specific, and not simply an elevation of plasma copper-containing oxidative enzymes. Increases in ceruloplasmin may result in increased levels of copper, which ultimately proves deleterious in schizophrenia.