Enteric alpha-synuclein expression is increased in Parkinson's disease but not Alzheimer's disease

Background and Objective Alpha-synuclein (-Syn) is immunohistochemically detectable in enteric neurons in some subjects. We determined its age distribution in the general autopsy population and in an age-matched subset investigated differences with Parkinson's (PD) and Alzheimer's diseases (AD). Methods Archival autopsy samples of colon from 95 cases (77 general population, 10 PD, and 8 AD) were immunostained with monoclonal antibody KM51. -Syn detectability was semiquantitatively graded 1 to 3. Results -Syn was detectable in 52% of the general population, and its level of expression did not change between ages 40 and 91. All PD subjects were -Syn positive, with higher prevalence (P = 0.001) and grade (P = 0.003) than age-matched controls. AD subjects were no more likely to be -Syn positive or have a higher grade than controls. Conclusions Either PD develops selectively in the enterically -Syn-positive population subset or PD induces this expression. Absence of increased -Syn expression in AD points to differences in pathogenesis. (c) 2013 Movement Disorder Society