Copper neurotoxicity is dependent on dopamine‐mediated copper uptake and one‐electron reduction of aminochrome in a rat substantia nigra neuronal cell line

• Published in: Journal of neurochemistry Vol. 77; no. 2; pp. 519 - 529
• Main Authors: Paris, Irmgard, Dagnino‐Subiabre, Alexies, Marcelain, Katherine, Bennett, Lori B., Caviedes, Pablo, Caviedes, Raúl, Azar, Claudio Olea, Segura‐Aguilar, Juan
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.04.2001; Blackwell
• Subjects: aminochrome; Animals; Biological and medical sciences; Catalase - biosynthesis; Catalase - genetics; Cell Line; Chemical and industrial products toxicology. Toxic occupational diseases; copper; Copper Sulfate - metabolism; Copper Sulfate - pharmacology; Copper Sulfate - toxicity; Dicumarol - toxicity; dopamine; Dopamine - pharmacology; DT‐diaphorase; Electron Spin Resonance Spectroscopy; Enzyme Induction - drug effects; free radicals; Glutathione Peroxidase - biosynthesis; Glutathione Peroxidase - genetics; Indolequinones; Indoles - metabolism; Ion Transport - drug effects; Medical sciences; Metallothionein - metabolism; Metals and various inorganic compounds; NAD(P)H Dehydrogenase (Quinone) - biosynthesis; NAD(P)H Dehydrogenase (Quinone) - genetics; Neurons - drug effects; Neurons - metabolism; Nomifensine - pharmacology; Oxidation-Reduction; Oxidative Stress; Parkinson Disease - metabolism; quinones; Rats; RNA, Messenger - biosynthesis; Substantia Nigra - cytology; Superoxide Dismutase - biosynthesis; Superoxide Dismutase - genetics; Toxicology; Rat; Toxicity; Rodentia; Central nervous system; Metal; Inorganic element; Vertebrata; Mammalia; Cell line; Locus niger; Copper; Mechanism of action; Brain (vertebrata)
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.2001.00243.x

The mechanism of copper (Cu) neurotoxicity was studied in the RCSN‐3 neuronal dopaminergic cell line, derived from substantia nigra of an adult rat. The formation of a Cu–dopamine complex was accompanied by oxidation of dopamine to aminochrome. We found that the Cu–dopamine complex mediates the uptake of 64CuSO4 into the Raúl Caviedes substantia nigra‐clone 3 (RCSN3) cells, and it is inhibited by the addition of excess dopamine (2 m m) (63%, p < 0.001) and nomifensine (2 µm) (77%, p < 0.001). Copper sulfate (1 m m) alone was not toxic to RCSN‐3 cells, but was when combined with dopamine or with dicoumarol (95% toxicity; p < 0.001) which inhibits DPNH and TPNH (DT)‐diaphorase. Electron spin resonance (ESR) spectrum of the 5,5‐dimethylpyrroline‐N‐oxide (DMPO) spin trap adducts showed the presence of a C‐centered radical when incubating cells with dopamine, CuSO4 and dicoumarol. A decrease in the expression of CuZn‐superoxide dismutase and glutathione peroxidase mRNA was observed when RCSN‐3 cells were treated with CuSO4, dopamine, or CuSO4 and dopamine. However, the mRNA expression of glutathione peroxidase remained at control levels when the cells were treated with CuSO4, dopamine and dicoumarol. The regulation of catalase was different since all the treatments with CuSO4 increased the expression of catalase mRNA. Our results suggest that copper neurotoxicity is dependent on: (i) the formation of Cu–dopamine complexes with concomitant dopamine oxidation to aminochrome; (ii) dopamine‐dependent Cu uptake; and (iii) one‐electron reduction of aminochrome.