Interaction of Human Substantia Nigra Neuromelanin with Lipids and Peptides

Abstract

Neuromelanin was isolated from human substantia nigra using different procedures. In the pigment isolated by any of these procedures a peptide component covalently bound to the melanic structure was found, as shown by treatment with reagents known to eliminate noncovalently bound proteins. The amino acid content of such a peptide component was reproducible and corresponded to ϳ15% of the neuromelanin weight. Neuromelanin also showed the ability to absorb specifically lipid molecules, ϳ20% of its weight, and among these lipids cholesterol was identified, constituting ϳ5% of the total lipid mixture. A synthetic melanin, incubated with putamen homogenate, bound tissue peptides with an amino acid content quite close to that of neuromelanin. The same synthetic melanin adsorbed a lower amount of lipids from the putamen homogenate compared with neuromelanin. The sulfur content of neuromelanin was also reproducible even using different isolation procedures. A nonpigmented tissue like corpus callosum was used as a control and extracted by the method used for neuromelanin isolation; a total elimination of tissue components was found, thus demonstrating the capability of the reported procedures to isolate neuromelanin alone. The presence of a peptide component in the neuromelanin structure and the selective affinity for lipid molecules suggest new aspects of the functional role and metabolic pathway of neuromelanin.

New melanic pigments in the human brain that accumulate in aging and block environmental toxic metals

“…For the sake of simplicity and classification, in the ensuing discussion all of these pigments from the different brain regions studied will be termed ''neuromelanins,'' to embrace a family of pigments, including both those described here and those we characterized in substantia nigra and locus coeruleus (2,15). Neuromelanins appear to be ubiquitous in the human brain and are contained in high concentrations, ranging from 0.2 to 3.5 mg/g tissue in the largest areas like putamen, premotor cortex, and cerebellum, in addition to substantia nigra.…”

“…The pigments from organelles of the same brain regions were isolated and purified in amounts sufficient for accurate structural determinations and for comparison with neuromelanin from substantia nigra (2,15). For isolation of the pigments, tissues from brain areas were washed with phosphate buffer and SDS and successively treated with proteinase to remove proteins and methanol/hexane to remove lipids.…”

“…Pheomelanin is generated by oxidation of cysteinyl-dopamine (Cys-DA) and contains benzothiazine groups. In addition to the mentioned melanic component of neuromelanin, there are also poorly-characterized peptide and aliphatic components (15).…”

The role of polyunsaturated fatty acids in restoring the aging neuronal membrane

“…As an example, in the analysis of the CRF-ACTH-steroids axis, P450 [73,135] and cholesterol metabolism have been shown to exert profound effects on dopamine at the beginning of the axis, and on steroids at the end of the axis. Prostaglandins are derivatives of fatty acids, but their metabolism is modulated by P450.…”

Neuromelanin selectively induces apoptosis in dopaminergic SH‐SY5Y cells by deglutathionylation in mitochondria: involvement of the protein and melanin component

“…In addition, protein, lipids, and trace metals are detected in NM, but it has never been clarified whether these components are integrated in a complex structure of NM or only associated to melanin in NM granules. NM contains protein components of about 15% of NM mass (Gerlach et al 1995;Zecca et al 2000). Proteomics of NM granules identified about 70 proteins occurring commonly in human brain tissues, mainly lysosomal proteins, suggesting non-selective protein binding to DA quinone (Tribl et al 2005).…”