Apoptotic-like changes in Lewy-body-associated disorders and normal aging in substantia nigral neurons

In Parkinson's disease and other Lewy-body-associated disorders, the substantia nigra pars compacta undergoes degeneration, but the mechanism of cell death has not been previously described. The substantia nigra of normal and Alzheimer's disease cases were compared with substantia nigra from patients with Lewy-body-associated disorders (Parkinson's disease, concomitant Alzheimer's/Parkinson's disease, and diffuse Lewy body disease) using in situ end labeling to detect fragmented DNA. In situ end-labeled neurons demonstrated changes resembling apoptosis: nuclear condensation, chromatin fragmentation, and formation of apoptotic-like bodies. Ultrastructural analysis confirmed nuclear condensation and formation of apoptotic-like bodies. Apoptotic-like changes were seen in the substantia nigra of both normal and diseased cases; concomitant Alzheimer's/Parkinson's disease and diffuse Lewy body disease cases had significantly higher amounts of apoptotic-like changes than normal controls or Alzheimer patients. The finding of neuronal death by apoptosis may have relevance for the development of new treatment strategies for Parkinson's disease and related disorders.