Progressive supranuclear palsy (PSP) is an atypical parkinsonian syndrome based on tau pathology; its clinical phenotype differs, but PSP with Richardson's syndrome (PSP-RS) and the PSP parkinsonism predominant (PSP-P) variant remain the two most common manifestations. Neuroinflammation is involved in the course of the disease and may cause neurodegeneration. However, an up-to-date cytokine profile has not been assessed in different PSP phenotypes. This study aimed to evaluate possible differences in neuroinflammatory patterns between the two most common PSP phenotypes. Serum and cerebrospinal fluid (CSF) concentrations of interleukin-1 beta (IL-1β) and IL-6 were analyzed using enzyme-linked immunosorbent assay (ELISA) kits in 36 study participants-12 healthy controls and 24 patients with a clinical diagnosis of PSP-12 PSP-RS and 12 PSP-P. Disease duration among PSP patients ranged from three to six years. All participants underwent basic biochemical testing, and neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) values were calculated. Due to a lack of neuropathological examinations, as all patients remain alive, total tau levels were assessed in the CSF. Tau levels were significantly higher in the PSP-P and PSP-RS groups compared to the healthy controls. The lowest concentrations of serum and CSF interleukins were observed in PSP-RS patients, whereas PSP-P patients and healthy controls had significantly higher interleukin concentrations. Furthermore, there was a significant correlation between serum IL-6 levels and PLR in PSP-RS patients. The results indicate the existence of distinct neuroinflammatory patterns or a neuroprotective role of increased inflammatory activity, which could cause the differences between PSPS phenotypes and clinical course. The causality of the correlations described requires further studies to be confirmed.
Keywords: PSP-P; PSP-RS; atypical parkinsonian syndrome; clinical phenotype; neuroinflammation; progressive supranuclear palsy.