Silver stainings distinguish Lewy bodies and glial cytoplasmic inclusions: comparison between Gallyas-Braak and Campbell-Switzer methods

Lewy bodies (LBs) of idiopathic Parkinson’s disease and glial cytoplasmic inclusions (GCIs) of multiple system atrophy are pathological deposits both composed of phosphorylated α-synuclein woven into different filaments. Although both LBs and GCIs are considered to be hallmarks for each independent synucleinopathy, until now they could not be clearly distinguished on the basis of their biochemical or immunohistochemical features. We have examined possible differences in their argyrophilic features and their relation to synuclein-like or ubiquitin-like immunoreactivity (IR). Pairs of mirror sections from different brain areas were triple-fluorolabeled with an anti-α-synuclein antibody, an anti-ubiquitin antibody and thiazin red (TR), a fluorochrome that labels fibrillary structures such as Lewy bodies or neurofibrillary tangles. One of the paired sections was subsequently stained using the Campbell-Switzer method (CS), and the other by the Gallyas-Braak method (GB). By comparing of the same microscopic field on the paired fluorolabeled sections, subsequently silver-stained with either CS or GB, five different profiles of each structure could be determined: α-synuclein-like IR, ubiquitin-like IR, affinity to TR, argyrophilia with CS or GB. GCIs exhibited argyrophilia with both CS and GB but lacked affinity to TR. In contrast, LBs exhibited argyrophilia with CS but not with GB and some affinity to TR. These disease-specific profiles of argyrophilia were consistent, and were not influenced by areas or cases examined. Although immunohistochemical features of LBs and GCIs were similar in exhibiting IR for α-synuclein and ubiquitin, the contrast in their argyrophilic profiles may indicate possible differences in the molecular composition or conformation of α-synuclein. Even though these empirical differences still remain to be explained, awareness of this clear distinction is potentially of diagnostic and pathological relevance.