Isolation and C-13-NMR characterization of an insoluble proteinaceous fraction from substantia nigra of patients with Parkinson's disease

Neuromelanin is a dark brown pigment suspected of being involved in the pat hogenesis of Parkinson's disease. This pigment can be isolated from normal human substantia nigra by a procedure that includes an extensive proteolyti c treatment. In this study we used such a procedure to extract the neuromel anin pigment from a pool of substantia nigra from patients affected by Park inson's disease. C-13 Cross polarization magic angle spinning nuclear magne tic resonance spectroscopy and electron paramagnetic resonance spectroscopy were used to characterize the solid residue obtained from the extraction p rocedure. We found that the pigment extracted from the substantia nigra of parkinsonian patients was mainly composed of highly cross-linked, protease- resistant, lipo-proteic material, whereas the neuromelanin macromolecule ap pears to be only a minor component of this extract. A synthetic model of me lanoprotein has been prepared by enzymatic oxidation of dopamine in the pre sence of albumin. Once it has undergone the same proteolytic treatment, thi s model system yields a C-13-NMR spectrum which is similar to that observed for the parkinsonian midbrain extract. These results an consistent with th e view that oxidative stress has a relevant role in the pathogenesis of Par kinson's disease.