Novel Nasal Epithelial Cell Markers of Parkinson's Disease Identified Using Cells Treated with alpha-Synuclein Preformed Fibrils

Abstract

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, characterized by olfactory dysfunction in the early stages. alpha-Synuclein pathologies in the olfactory organs are shown to spread to the brain through the nose-brain axis. We first developed a nasal epithelial PD cellular model by treating RPMI-2650 cells with alpha-synuclein preformed fibrils (PFF). Upon uptake of PFF, RPMI-2650 cells showed mitochondrial proteome alteration and downregulation of parkin, which has previously been identified as a nasal biomarker of PD. Functional cluster analysis of differentially expressed genes in RPMI-2650 cells revealed various pathways affected by alpha-synuclein pathology, including the detection of chemical stimulus involved in sensory perception, olfactory receptor activity, and sensory perception of smell. Among genes that were most affected, we validated, by real-time quantitative PCR, the downregulation ofMAP3K8,OR10A4,GRM2,OR51B6, andOR9A2,as well as upregulation ofIFIT1B,EPN1, OR1D5, LCN, and OTOL1in PFF-treated RPMI-2650 cells. Subsequent analyses of clinical samples showed a downregulation ofOR10A4andOR9A2transcripts and an upregulation ofIFIT1Bin cells isolated from the nasal fluid of PD patients, as compared to those from the controls (cutoff value = 0.5689 forOR9A2,with 72.4% sensitivity and 75% specificity, and 1.4658 forIFIT1B,with 81.8% sensitivity and 77.8% specificity). Expression levels of these nasal PD markers were not altered in nasal fluid cells from SWEDD (scans without evidence of dopaminergic deficits) patients with PD-like motor symptoms. These nasal markers were significantly altered in patients of PD with hyposmia compared to the control hyposmic subjects. Our results validated the alpha-synuclein-treated nasal epithelial cell model to identify novel biomarkers for PD and suggest the utility of olfactory transcripts, along with olfactory dysfunction, in the diagnosis of PD.