Proteomic Profile of Saliva in Parkinson's Disease Patients: A Proof of Concept Study

Abstract

Parkinson's disease (PD) is a progressive neurodegenerative disorder. It affects many organs. Lewy bodies-a histopathological "hallmark" of PD-are detected in about 75% of PD submandibular gland samples. We hypothesize that saliva can be a source of biomarkers of PD. The aim of the study was to evaluate and compare the salivary proteome of PD patients and healthy controls (HC). Salivary samples from 39 subjects (24 PD patients, mean age 61.6 ± 8.2; 15 HC, mean age 60.9 ± 6.7) were collected. Saliva was collected using RNA-Pro-Sal kits. Label-free LC-MS/MS mass spectrometry was performed to characterize the proteome of the saliva. IPA analysis of upstream inhibitors was performed. A total of 530 proteins and peptides were identified. We observed lower concentrations of S100-A16, ARP2/3, and VPS4B in PD group when compared to HC. We conclude that the salivary proteome composition of PD patients is different than that of healthy controls. We observed a lower concentration of proteins involved in inflammatory processes, exosome formation, and adipose tissue formation. The variability of expression of proteins between the two groups needs to be considered.

Keywords: Parkinson’s disease; neurodegeneration; proteomic profile; saliva; salivary glands.

Figure 1

Area under the curve (AUC) receiver operating characteristic curve (ROC) analysis for S100A16 and ARPC1A proteins in HC versus PD patients.

Figure 2

A volcano plot from the mass spectrometry data is shown. The x-axis shows the fold change values and the y axis shows the −log₁₀ p-values showing statistical significance. Q96FQ6–S100A16 protein; Q92747–ARPC1A protein; O75351–VPS4B protein. The horizontal dashed line shows where p = 0.05 (−log₁₀(0.05)~ = 1.3) is, while the vertical dashed line shows where the fold change is 1.5 (log₂ (1.5)~ = 0.58). The absolute 1.5-fold change and p-value of 0.05 are used as the threshold cutoff.