Features of ceruloplasmin in the cerebrospinal fluid of Alzheimer’s disease patients

Abstract

The level of the apo-form of the copper enzyme ceruloplasmin (CP) is an established peripheral marker in diseases associated with copper imbalance. In view of the proposal that disturbances of copper homeostasis may contribute to neurodegeneration associated with Alzheimer's disease (AD), the present work investigates, by Western blot and non-reducing SDS-PAGE followed by activity staining, the features of CP protein, and the copper/CP relationship in cerebrospinal fluid (CSF) and serum of AD patients. Results show that only a fraction of total copper is associated with CP in the CSF, at variance with serum, both in affected and in healthy individuals. Furthermore, a conspicuous amount of apo-ceruloplasmin and a decrease of CP oxidase activity characterize the CSF of the affected individuals, and confirm that an impairment of copper metabolism occurs in their central nervous system. In the CSF of AD patients the decrease of active CP, associated with the increase in the pool of copper not sequestered by this protein, may play a role in the neurodegenerative process.

P2X7 Receptor-mediated Scavenger Activity of Mononuclear Phagocytes toward Non-opsonized Particles and Apoptotic Cells Is Inhibited by Serum Glycoproteins but Remains Active in Cerebrospinal Fluid

“…7d) confirmed that phagocytosis was unimpeded by CSF and that purified CP and APP, which are largely excluded from CSF, remained inhibitory to phagocytosis in the CSF medium. Interestingly, all three inhibitory glycoproteins identified in this study have also been implicated in neurodegeneration, particularly Alzheimer disease (37,38). Our identification of CP, SAP, and APP as inhibitory proteins for phagocytosis of apoptotic cells mediated by P2X7 or other scavenger receptors may provide new insights into the pathogenesis of neurodegenerative disease.…”

Ceruloplasmin fragmentation is implicated in 'free' copper deregulation of Alzheimer disease

“…The spots at high molecular weight (135-115 kDa) of the fully denatured protein that we show in this study may represent a pool of the two forms, as we have recently shown in a dedicated study, revealing a conspicuous amount of apo-ceruloplasmin in the CSF of AD patients. 20 The evidence of low-molecular-weight fragments of ceruloplasmin in AD samples suggests that at least a portion of this protein is present in its apoform in general circulation, and indicates that an impairment in the incorporation of copper into the protein may occur in AD during ceruloplasmin biosynthesis. In fact, the six integral copper atoms are incorporated into ceruloplasmin during its biosynthesis through the copper-transporting ATPase ATP7B in the secretory compartment of the liver.…”

“…5,6 In particular, our recent biochemical studies demonstrated that a discrete concentration increase of copper occurs in AD which exceeds the amount of ceruloplasmin, 15 and that a considerable amount of inactive ceruloplasmin can be detected in the cerebrospinal fluid of AD patients. 20 Since ceruloplasmin is the main copper transporter in general circulation, we aimed in the present work at studying the qualitative changes occurring in the ceruloplasmin present in the serum of AD patients, explored by means of a two dimensional polyacrylamide gel electrophoresis (2-D PAGE) approach, to detect possible protein modifications that can be considered explanatory of 'free' copper deregulation.…”

Biomarkers for the early diagnosis of Alzheimer’s disease: The challenge of XXI century

“…It has been hypothesised that the increased "free" copper found in AD was due to a defect in copper incorporation into ceruloplasmin. This hypothesis was supported by: 1) the increased levels of serum apoceruloplasmin derived by the failure of copper binding into ceruloplasmin during its biosynthesis in the liver; 2) liver dysfunction due to "free" copper disturbance of hepatocytes; 3) evidence of the move of "free" copper from the serum to the CSF, overcoming BBB, and of "free" copper interaction with CSF markers of AD [52][53][54][55][56][57].…”

“…85% -95% of the serum copper is tightly bound to ceruloplasmin while the resting "free" copper is bound to albumin, alpha 2 macroglobulin, and low-molecularweight compounds such as peptides and amino acids. The difference between the two copper pools is that the "free" copper overcomes BBB [52,53]. Moreover, in AD patients "free" copper is increased in CSF [54] and in brain parenchyma.…”