title: Neuromelanins of human brain have soluble and insoluble components with dolichols attached to the melanic structure.
abstract: Neuromelanins (NMs) are neuronal pigments of melanic-lipidic type which accumulate during aging. They are involved in protective and degenerative mechanisms depending on the cellular context, however their structures are still poorly understood. NMs from nine human brain areas were analyzed in detail. Elemental analysis led to identification of three types of NM, while infrared spectroscopy showed that NMs from neurons of substantia nigra and locus coeruleus, which selectively degenerate in Parkinson's disease, have similar structure but different from NMs from brain regions not targeted by the disease. Synthetic melanins containing Fe and bovine serum albumin were prepared to model the natural product and help clarifying the structure of NMs. Extensive nuclear magnetic resonance spectroscopy studies showed the presence of dolichols both in the soluble and insoluble parts of NM. Diffusion measurements demonstrated that the dimethyl sulfoxide soluble components consist of oligomeric precursors with MWs in the range 1.4-52 kDa, while the insoluble part contains polymers of larger size but with a similar composition. These data suggest that the selective vulnerability of neurons of substantia nigra and locus coeruleus in Parkinson's disease might depend on the structure of the pigment. Moreover, they allow to propose a pathway for NM biosynthesis in human brain.
authors.affiliation: Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy.
authors.forename: Mireille
authors.initials: M
authors.lastname: Engelen
authors.forename: Renzo
authors.initials: R
authors.lastname: Vanna
authors.forename: Chiara
authors.initials: C
authors.lastname: Bellei
authors.forename: Fabio A
authors.initials: FA
authors.lastname: Zucca
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Wakamatsu
authors.forename: Enrico
authors.initials: E
authors.lastname: Monzani
authors.forename: Shosuke
authors.initials: S
authors.lastname: Ito
authors.forename: Luigi
authors.initials: L
authors.lastname: Casella
authors.forename: Luigi
authors.initials: L
authors.lastname: Zecca
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D002244:Carbon / Q000378:metabolism; D002417:Cattle; D004058:Diffusion; D004286:Dolichols / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008543:Melanins / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009584:Nitrogen / Q000378:metabolism; D012995:Solubility; D012996:Solutions; D013055:Spectrophotometry, Infrared
chemical_list: D000596:Amino Acids; D004286:Dolichols; D008543:Melanins; D012996:Solutions; C014121:neuromelanin; D002244:Carbon; D009584:Nitrogen