The role of subcutaneous adipose tissue in supporting the copper balance in rats with a chronic deficiency in holo-ceruloplasmin

Lipid dysmetabolism in ceruloplasmin-deficient mice revealed both in vivo and ex vivo by MRI, MRS and NMR analyses

Ceruloplasmin (Cp) is a ferroxidase that plays a role in cellular iron homeostasis and is mainly expressed in the liver and secreted into the blood. Cp is also produced by adipose tissue, which releases it as an adipokine. Although a dysfunctional interaction of iron with the metabolism of lipids has been associated with several metabolic diseases, the role of Cp in adipose tissue metabolism and in the interplay between hepatocytes and adipocytes has been poorly investigated. We previously found that Cp-deficient (CpKO) mice become overweight and demonstrate adipose tissue accumulation together with liver steatosis during aging, suggestive of lipid dysmetabolism. In the present study, we investigated the lipid alterations which occur during aging in adipose tissue and liver of CpKO and wild-type mice both in vivo and ex vivo. During aging of CpKO mice, we observed adipose tissue accumulation and liver lipid deposition, both of which are associated with macrophage infiltration. Liver lipid deposition was characterized by accumulation of triglycerides, fatty acids and ω-3 fatty acids, as well as by a switch from unsaturated to saturated fatty acids, which is characteristic of lipid storage. Liver steatosis was preceded by iron deposition and macrophage infiltration, and this was observed to be already occurring in younger CpKO mice. The accumulation of ω-3 fatty acids, which can only be acquired through diet, was associated with body weight increase in CpKO mice despite food intake being equal to that of wild-type mice, thus underlining the alterations in lipid metabolism/catabolism in Cp-deficient animals.

Chemical background of silver nanoparticles interfering with mammalian copper metabolism

The rapidly increasing application of silver nanoparticles (AgNPs) boosts their release into the environment, which raises a reasonable alarm for ecologists and health specialists. This is manifested as increased research devoted to the influence of AgNPs on physiological and cellular processes in various model systems, including mammals. The topic of the present paper is the ability of silver to interfere with copper metabolism, the potential health effects of this interference, and the danger of low silver concentrations to humans. The chemical properties of ionic and nanoparticle silver, supporting the possibility of silver release by AgNPs in extracellular and intracellular compartments of mammals, are discussed. The possibility of justified use of silver for the treatment of some severe diseases, including tumors and viral infections, based on the specific molecular mechanisms of the decrease in copper status by silver ions released from AgNPs is also discussed.

Influence of Silver Nanoparticles on the Growth of Ascitic and Solid Ehrlich Adenocarcinoma: Focus on Copper Metabolism

The link between copper metabolism and tumor progression motivated us to use copper chelators for suppression of tumor growth. We assume that silver nanoparticles (AgNPs) can be used for lowering bioavailable copper. Our assumption is based on the ability of Ag(I) ions released by AgNPs in biological media and interfere with Cu(I) transport. Intervention of Ag(I) into copper metabolism leads to the replacement of copper by silver in ceruloplasmin and the decrease in bioavailable copper in the bloodstream. To check this assumption, mice with ascitic or solid Ehrlich adenocarcinoma (EAC) were treated with AgNPs using different protocols. Copper status indexes (copper concentration, ceruloplasmin protein level, and oxidase activity) were monitored to assess copper metabolism. The expression of copper-related genes was determined by real-time PCR in the liver and tumors, and copper and silver levels were measured by FAAS. Intraperitoneal AgNPs treatment beginning on the day of tumor inoculation enhanced mice survival, reduced the proliferation of ascitic EAC cells, and suppressed the activity of HIF1α, TNF-α and VEGFa genes. Topical treatment by the AgNPs, which was started together with the implantation of EAC cells in the thigh, also enhanced mice survival, decreased tumor growth, and repressed genes responsible for neovascularization. The advantages of silver-induced copper deficiency over copper chelators are discussed.

Properties of recombinant extracellular N-terminal domain of human high-affinity copper transporter 1 (hNdCTR1) and its interactions with Cu(II) and Ag(I) ions

High-affinity copper transporter 1 (CTR1) is a key link in the transfer of copper (Cu) from the extracellular environment to the cell. Violation in the control system of its expression, or mutations in this gene, cause a global copper imbalance. However, the mechanism of copper transfer via CTR1 remains unclear. It has been shown that transformed bacteria synthesizing the fused GB1-NdCTR become resistant to toxic silver ions. According to UV-Vis spectrophotometry and isothermal titration calorimetry, electrophoretically pure GB1-NdCTR specifically and reversibly binds copper and silver ions, and binding is associated with aggregation. Purified NdCTR1 forms SDS-resistant oligomers. The link between nontrivial properties of NdCTR1 and copper import mechanism from extracellular space, as well as potential chelating properties of NdCTR1, are discussed.

Reverse regulation of hepatic ceruloplasmin production in rat model of myocardial ischemia

BACKGROUND

Ceruloplasmin (Cp) is a major copper-binding protein produced in the liver and delivers copper to extrahepatic organs. Patients with myocardial infarction are often featured by an elevation of serum copper concentrations due to copper efflux from ischemic hearts. The present study was undertaken to test the hypothesis that serum copper elevation leads to up-regulation of hepatic Cp in myocardial infarction.

METHODS

Adult male Sprague-Dawley rats were subjected to left anterior descending (LAD) coronary artery ligation to induce myocardial infarction. Serum copper and Cp levels, as well as changes in hepatic Cp and copper-transporting P-type ATPase (Atp7b), were determined from blood and liver samples collected on day 1, 4, or 7 after the operation.

RESULTS

Serum copper concentrations were significantly increased on day 4 after LAD ligation, accompanied by an increase in serum Cp levels and activities. Concomitantly, the protein levels of Cp and copper exporter, Atp7b, were also significantly increased in the liver. Furthermore, inhibiting the increase of serum copper by a copper chelator, triethylenetetramine (TETA), effectively abolished the elevated Cp activity after LAD ligation.

CONCLUSION

These results indicate that serum Cp elevation in response to myocardial ischemia most likely resulted from the increased hepatic Cp production, which in turn was more responsive to serum copper elevation than inflammatory response following myocardial ischemia.

Silver Ions as a Tool for Understanding Different Aspects of Copper Metabolism

In humans, copper is an important micronutrient because it is a cofactor of ubiquitous and brain-specific cuproenzymes, as well as a secondary messenger. Failure of the mechanisms supporting copper balance leads to the development of neurodegenerative, oncological, and other severe disorders, whose treatment requires a detailed understanding of copper metabolism. In the body, bioavailable copper exists in two stable oxidation states, Cu(I) and Cu(II), both of which are highly toxic. The toxicity of copper ions is usually overcome by coordinating them with a wide range of ligands. These include the active cuproenzyme centers, copper-binding protein motifs to ensure the safe delivery of copper to its physiological location, and participants in the Cu(I) ↔ Cu(II) redox cycle, in which cellular copper is stored. The use of modern experimental approaches has allowed the overall picture of copper turnover in the cells and the organism to be clarified. However, many aspects of this process remain poorly understood. Some of them can be found out using abiogenic silver ions (Ag(I)), which are isoelectronic to Cu(I). This review covers the physicochemical principles of the ability of Ag(I) to substitute for copper ions in transport proteins and cuproenzyme active sites, the effectiveness of using Ag(I) to study copper routes in the cells and the body, and the limitations associated with Ag(I) remaining stable in only one oxidation state. The use of Ag(I) to restrict copper transport to tumors and the consequences of large-scale use of silver nanoparticles for human health are also discussed.