Investigation on Abnormal Iron Metabolism and Related Inflammation in Parkinson Disease Patients with Probable RBD

Objective To investigate potential mechanisms involving abnormal iron metabolism and related inflammation in Parkinson disease (PD) patients with probable rapid eye movement sleep behavior disorder (PRBD). Methods Total 210 PD patients and 31 controls were consecutively recruited. PD patients were evaluated by RBD Screening Questionnaire (RBDSQ) and classified into PRBD and probable no RBD (NPRBD) groups. Demographics information were recorded and clinical symptoms were evaluated by series of rating scales. Levels of iron and related proteins and inflammatory factors in cerebrospinal fluid (CSF) and serum were detected. Comparisons among control, NPRBD and PRBD groups and correlation analyses between RBDSQ score and levels of above factors were performed. Results (1) The frequency of PRBD in PD patients is 31.90%. (2) PRBD group has longer disease duration, more advanced disease stage, severer motor symptoms and more non-motor symptoms than NPRBD group. (3) In CSF, levels of iron, transferrin, NO and IL-1 beta in PRBD group are prominently increased. RBDSQ score is positively correlated with the levels of iron, transferrin, NO and IL-1 beta in PD group. Iron level is positively correlated with the levels of NO and IL-1 beta in PD group. (4) In serum, transferrin level is prominently decreased in PRBD group. PGE(2) level in PRBD group is drastically enhanced. RBDSQ score exhibits a positive correlation with PGE(2) level in PD group. Conclusions PRBD is common in PD patients. PRBD group has severer motor symptoms and more nonmotor symptoms. Excessive iron in brain resulted from abnormal iron metabolism in central and peripheral systems is correlated with PRBD through neuroinflammation.