3-nitrotyrosine and Lewy-Body-Disease

The synucleinopathies are a group of neurodegenerative disorders characterized by the presence of alpha-synuclein inclusions in neurons (Lewy body diseases, LBD) or glial cells (multiple system atrophies, MSA). Recently, nitration of alpha-synuclein has been reported as the possible modification that induces its aggregation and deposition in these disorders. In this study we investigated the distribution and relationships of alpha-synuclein inclusions and 3-nitrotyrosine (3-NT), a marker of protein nitration through oxidative mechanisms, in brains diagnosed with LBD or MSA and control brains using double immunohistochemical techniques. In LBD cases, 3-NT colocalized with alpha-synuclein immunoreactivity in classic and cortical Lewy bodies and in dystrophic neurites in substantia nigra. However, most pale bodies and diffuse deposits in substantia nigra and Lewy neurites in hippocampus lack 3-NT immunoreactivity. A majority of cases showed diffuse cytoplasmic 3-NT staining in pyramidal cells of the CA2-3 regions of the hippocampus that was independent of alpha-synuclein deposits. All MSA cases showed 3-NT immunoreactivity in glial inclusions. 3-NT neuronal staining was restricted to pontine nuclei with three cases showing nuclear and one case cytoplasmic staining. There was no colocalization of 3-NT nuclear immunoreactivity with alpha-synuclein-immunopositive nuclear inclusions in pontine neurons. These data show that protein nitration in LBD and MSA cases has a widespread distribution and is not only associated with the alpha-synuclein deposits. The presence of alpha-synuclein-positive deposits lacking 3-NT immunoreactivity suggests that nitration is not a prerequisite for alpha-synuclein deposition.

Topics: Aged; alpha-Synuclein; Brain; Cell Nucleus; Female; Humans; Inclusion Bodies; Lewy Bodies; Lewy Body Disease; Male; Middle Aged; Nerve Tissue Proteins; Neurites; Neuroglia; Neurons; Nitrates; Oxidative Stress; Striatonigral Degeneration; Synucleins; Tyrosine

Aggregated alpha-synuclein proteins form brain lesions that are hallmarks of neurodegenerative synucleinopathies, and oxidative stress has been implicated in the pathogenesis of some of these disorders. Using antibodies to specific nitrated tyrosine residues in alpha-synuclein, we demonstrate extensive and widespread accumulations of nitrated alpha-synuclein in the signature inclusions of Parkinson's disease, dementia with Lewy bodies, the Lewy body variant of Alzheimer's disease, and multiple system atrophy brains. We also show that nitrated alpha-synuclein is present in the major filamentous building blocks of these inclusions, as well as in the insoluble fractions of affected brain regions of synucleinopathies. The selective and specific nitration of alpha-synuclein in these disorders provides evidence to directly link oxidative and nitrative damage to the onset and progression of neurodegenerative synucleinopathies.

Topics: alpha-Synuclein; Alzheimer Disease; Antibodies, Monoclonal; Blotting, Western; Brain; Brain Chemistry; Enzyme-Linked Immunosorbent Assay; Fluorescent Antibody Technique; Humans; Immunohistochemistry; Lewy Bodies; Lewy Body Disease; Microscopy, Immunoelectron; Multiple System Atrophy; Nerve Tissue Proteins; Neurodegenerative Diseases; Neurons; Oxidative Stress; Parkinson Disease; Synucleins; Tyrosine