Differential profiles of serum cytokines in Parkinson's disease according to disease duration

Objective: Neurodegeneration and neuroinflammation are two intertwined mechanisms contributing to the pathophysiology of Parkinson's disease. Whether circulating biomarkers reflecting those two processes differ according to disease duration remains to be established. The present study was conducted to characterize the biomarkers individuals with PD with short (<= 5 years) or long disease duration (>5 years).Methods: We consecutively enrolled 104 patients with Parkinson's disease and evaluated them using validated clinical scales (MDS-UPDRS, Hoehn and Yahr staging, MMSE). Serum samples were assayed for the following biomarkers: neurofilament light chain (NfL), brain-derived neurotrophic factor (BDNF), interleukin (IL-) 1 beta, 4, 5, 6, 10, 17, interferon-gamma, and tumor necrosis factor alpha.Results: Mean age of participants was 66.0 +/- 9.6 years and 45 (34%) were women. The average disease duration was 8 +/- 5 years (range 1 to 19 years). Patients with short disease duration (<= 5 years) showed a pro-inflammatory profile, with significantly higher levels of pro-inflammatory IL-1 beta and lower concentrations of IL-5, IL-10 and IL-17 (p < 0.05). NfL serum levels showed a positive correlation with disease duration and age (respectively rho = 0.248, p = 0.014 and rho = 0.559, p < 0.001) while an opposite pattern was detected for BDNF (respectively rho-0,187, p = 0.034 and rho =-0.245, p = 0.014).Conclusions: Our findings suggest that a pro-inflammatory status may be observed in PD patients in the early phases of the disease, independently from age.