Alpha-Synuclein aggregation in pathological aging and Alzheimer's disease: the impact of beta-amyloid plaque level.

In central nervous system diseases, abnormal aggregation of one protein is often associated with aggregation of other proteins. To begin to assess whether beta-amyloid (Abeta) is associated with alpha-synuclein (AS) aggregation [secondary Lewy body (LB) formation], we used immunohistochemical techniques to compare the amygdala of 11 subjects with pathological aging and 18 with Alzheimer's disease. Overall, Abeta-40 plaque level was greater in cases with secondary AS aggregates. Abeta-42 plaque level was not associated with AS aggregation. Abeta-40 plaque levels cannot be ruled out as a factor involved in secondary LB formation.