Phosphorylated α-synuclein-immunoreactive retinal neuronal elements in Parkinson's disease subjects

• Published in: Neuroscience letters Vol. 571; pp. 34 - 38
• Main Authors: Beach, Thomas G., Carew, Jeremiah, Serrano, Geidy, Adler, Charles H., Shill, Holly A., Sue, Lucia I., Sabbagh, Marwan N., Akiyama, Haruhiko, Cuenca, Nicolás
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 13.06.2014
• Subjects: Aged; Aged, 80 and over; alpha-Synuclein - metabolism; Autopsy; Case-Control Studies; Diagnosis; Female; Ganglion cell; Humans; Lewy body; Male; Melanopsin; Middle Aged; Nerve Fibers - metabolism; Parkinson Disease - metabolism; Parkinson Disease - pathology; Pathology; Retinal Neurons - metabolism; Retinal Neurons - ultrastructure; Pathology; Diagnosis; Autopsy; Melanopsin; Lewy body; Ganglion cell
• DOI: 10.1016/j.neulet.2014.04.027
• ISSN: 0304-3940; 1872-7972

•Structural and functional retinal changes are present in Parkinson's disease (PD).•Phosphorylated α-synuclein (psyn) is a specific biomarker of PD.•Psyn-immunoreactive nerve fibers were present in the retina in 7/9 subjects with PD.•Psyn-immunoreactive neuronal perikarya were present in 1 PD subject.•This pathology may contribute to structural and functional retinal changes in PD. Visual symptoms are relatively common in Parkinson's disease (PD) and optical coherence tomography has indicated possible retinal thinning. Accumulation of aggregated α-synuclein is thought to be a central pathogenic event in the PD brain but there have not as yet been reports of retinal synucleinopathy. Retinal wholemounts were prepared from subjects with a primary clinicopathological diagnosis of PD (N=9), dementia with Lewy bodies (DLB; N=3), Alzheimer's disease (N=3), progressive supranuclear palsy (N=2) as well as elderly normal control subjects (N=4). These were immunohistochemically stained with an antibody against α-synuclein phosphorylated at serine 129, which is a specific molecular marker of synucleinopathy. Phosphorylated α-synuclein-immunoreactive (p-syn IR) nerve fibers were present in 7/9 PD subjects and in 1/3 DLB subjects; these were sparsely distributed and superficially located near or at the inner retinal surface. The fibers were either long and straight or branching, often with multiple en-passant varicosities along their length. The straight fibers most often had an orientation that was radial with respect to the optic disk. Together, these features are suggestive of either retinopetal/centrifugal fibers or of ganglion cell axons. In one PD subject there were sparse p-syn IR neuronal cell bodies with dendritic morphology suggestive of G19 retinal ganglion cells or intrinsically photosensitive ganglion cells. There were no stained nerve fibers or other specific staining in any of the non-PD or non-DLB subjects. It is possible that at least some of the observed visual function impairments in PD subjects might be due to α-synucleinopathy.