Copper in human health: From COVID 19 to neurodegenerative diseases.

Copper (Cu) exists in two oxidation states Cu+I and Cu+II yielding formation of enzymes involved in biological processes. In higher concentrations, by oxidative process and ROS production, Cu is toxic towards plants, humans and animals livers as observed in Wilson disease or sheep scrapie. Fighting according to the Fenton reaction against bacteria and viruses, has been proposed as a mean of combatting nosocomial diseases and complementary to COVID19 vaccination. In humans, Cu is stocked in liver, muscle or bound to brain protein as ß-APP, tau-protein, α-synuclein, ubiquitin or prion which present antioxidant properties when Cu-bonded. In abnormal ß-sheet conformation, they can trigger neurodegenerative diseases such as Alzheimer(AD), Parkinson(PD) and ALS. In these diseases, blood copper increase correlated with brain copper decrease has been described. In AD, abnormal D-serine has been detected in blood and cerebrospinal fluid. D-glutamate and D-alanine blood levels have been found in AD and could also be controlled with Cu and ceruloplasmin in a possible disease screening test. This abnormal D-conformation might result from epimerization of physiologically L-conformation brain peptides into protease-resistant D-enantiomers. This has previously been experimentally demonstrated for Bovine Spongiform Encephalopathy in a free Cu reductive medium with UV-induced free radicals. The Cu brain protective effect against free radicals was restored with cupric addition in oxidizing medium. Cupric supplementation in the brain, might restore Cu protection and slow down neurodegenerative processes. To lower side effects, Cu amino-acid complexes able to cross the blood brain barrier might be suggested for a Cu transfer to the brain.