Widespread and abundant alpha-synuclein pathology in a neurologically unimpaired subject.

The intracytoplasmic aggregation of alpha-synuclein (alphaS) protein is a common denominator for a group of neurodegenerative disorders currently known as synucleinopathies. It is generally assumed that the incorporation of alphaS protein into compact inclusions compromises the function and viability of its host cell via mechanical disruption. Herein, we report a widespread and abundant alphaS pathology in an elderly subject, whose medical history gave no indication of any neurodegenerative disease. We compared neuronal and glial components in this neurologically unimpaired subject with a patient with a clinical syndrome of dementia with Lewy bodies (DLB) by using a range of antigenic determinants and an in situ end-labeling technique. We detected no differences in vascular pathologies, in gliosis, or in apoptosis that would have explained the incompatible clinical end-points. With respect to the Alzheimer's disease-related changes, the only differences noted were the beta-amyloid aggregates in the putamen found in the DLB patient alone. Our findings suggest that there must be some currently unidentified factors rather than alphaS-positive inclusions that are responsible for the neuronal dysfunction. The alphaS-positive inclusions may well represent detoxified reserves that cells can tolerate for years, and thus prevention of their development could actually accelerate the diseases process.