Pick's disease: α- and β-synuclein-immunoreactive Pick bodies in the dentate gyrus

Abstract.

Recent studies have shown that neurofibrillary tangles frequently coexist with α-synuclein (α-S)-positive fibrillary inclusions in the limbic system in Alzheimer's disease. To elucidate whether α-, β- and γ-S immunoreactivity is present in Pick bodies (PBs), we examined immunohistochemically and immunoelectron microscopically the brains from three patients with Pick's disease. Numerous PBs were distributed widely, and were occasionally immunoreactive for α-S and β-S, but not for γ-S in all three cases. However, these immunoreactive PBs were almost all restricted to the dentate gyrus. Despite the co-localization of phosphorylated tau and α-S or β-S (as evidenced by double-labeling immunohistochemistry), immunoelectron microscopy revealed that α-S and β-S immunoreactivity occurs in granular and vesicular structures, but not in filamentous structures. These findings suggest that α-S and β-S are up-regulated in the neuronal perikarya but they are not incorporated into the constituent filaments of PBs, and that the preferential distribution of α-S- and β-S-positive PBs in the dentate gyrus may represent the cellular response to PB formation in this particular system.