Is alpha-synuclein in the colon a biomarker for premotor Parkinson's disease? Evidence from 3 cases.

BACKGROUND: Despite clinicopathological evidence that Parkinson's disease (PD) may begin in peripheral tissues, identification of premotor Parkinson's disease is not yet possible. Alpha-synuclein aggregation underlies Parkinson's disease pathology, and its presence in peripheral tissues may be a reliable disease biomarker. OBJECTIVE: We sought evidence of alpha-synuclein pathology in colonic tissues before the development of characteristic Parkinson's disease motor symptoms. METHODS: Old colon biopsy samples were available for three subjects with PD. Biopsies were obtained 2-5 years before PD onset. We performed immunohistochemistry studies for the presence of alpha-synuclein and Substance P in these samples. RESULTS: All subjects showed immunostaining for alpha-synuclein (two, five and two years before first motor Parkinson's disease symptom). No similar alpha-synuclein immunostaining was seen in 23 healthy controls. Staining of samples for substance P suggested colocalization of alpha-synuclein and substance P in perikarya and neurites. CONCLUSIONS: This is the first demonstration of alpha-synuclein in colon tissue prior to onset of PD. Additional study is required to determine whether colonic mucosal biopsy may be a biomarker of premotor PD.