3. Immunofluorescence characterization of skin nerve misfolded α -synuclein in different synucleinopathies: A confocal study

摘要

Intraneural misfolded α -synuclein (syn) characterized different synucleinopathies such as pure autonomic failure (PAF), idiopathic Parkinson disease (IPD) and dementia with Lewy Bodies (DLB). The aim of this study is to characterize by immunofluorescence the skin intraneural α -synuclein (syn) deposits in PAF, IPD and DLB to ascertain conformation-specific differences which may justify a different clinical phenotype. We identified a total of 21 skin intraneural abnormal syn deposits in PAF (3 patients), 22 in IPD (8 patients) and 40 in DLB (7 patients). Ten healthy subjects were used controls. Skin biopsy was performed on proximal (C7 paravertebral) and distal (thigh and leg) sites. To characterize abnormal syn deposits we used primary antibodies against native α -synuclein (NAC) and against C-terminal α -synuclein epitopes involved in post-translational modifications such as phosphorylation at serine 129 (pS129) and tyrosine 125 (pY125), nitrate α -synuclein at tyr125-133 (nY125-133) and advanced glycation end products (AGEs). Furthermore, the mature amyloid α -synuclein fibrils were characterized by using a non-commercial antibody (Syn-F) and ubiquitin deposits were identified by a specific antibody (UBI). Antibody raised against pS129 disclosed abnormal skin nerves syn deposits in all patients and never in the control group. Abnormal pS129 syn deposits were often (80–90% of all analysed deposits) stained by the antibody recognizing a fibril conformation, seldom (around 40%) by native antibodies and very occasionally by antibodies against nY125-133. Furthermore, abnormal syn deposits were not stained by antibodies against pY125, AGEs and UBI. The immunofluorescence characterization of abnormal syn deposits showed similar findings in IPD, PAF and DLB although in these latter abnormal deposits were quantitatively higher than in IPD. Phosphorylation at serine 129 was the most sensitive and specific epitope to identify skin nerves abnormal syn deposits for the in vivo diagnosis of synucleinopathies; (2) skin syn neuritis showed no relevant immunofluorescence differences in PAF, IPD and DLB suggesting a similar conformation among different clinical phenotypes.