Expression of prion protein in the cerebrospinal fluid of patients with Parkinson's disease complicated with rapid eye movement sleep behavior disorder.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases and mainly manifests with decreasing numbers of dopaminergic neurons. Rapid eye movement (REM) sleep behavior disorder (RBD) has an incidence of 15-47% in all PD patients. Prion proteins (PrPs), which are expressed in both neurons and glial cells of the brain, are believed to be correlated with abnormal neurological functions, although their role in PD-related sleeping disorders remains unclear. We therefore investigated the expressional profiles of PrP in PD patients with RBD. Quantitative real-time polymerase chain reaction and western blotting were used to detect the mRNA and protein levels of PrP, respectively, in the cerebrospinal fluid (CSF) of PD patients with RBD, PD patients without sleeping disorder, and healthy people (N = 23 each). We investigated the correlation between the CSF PrP level and sleeping behavior in PD patients. Patients with PD complicated with RBD had significantly elevated CSF PrP expression levels (both mRNA and protein) compared with either PD patients without sleeping disorder or healthy individuals (P < 0.05 in both cases). There is elevated expression of PrP in the CSF of PD patients with RBD. This may benefit the diagnosis of PD-related RBD.