Objective: To delineate the impact of T helper 17 (Th17) pathway-related cytokines in the risk, severity and psychopathology of patients with Parkinson’s Disease (PD).

Background: PD is one of the most common extrapyramidal disorders, which leads to significant morbidity. Immune-inflammatory pathway has been implicated in the striato-nigral degeneration. Th17 cells, a relatively recently identified lineage of T helper cells, have emerged as a potential pathogenic player in many degenerative brain diseases. Th17 cells have robust functional implications in both the systemic and neuro-inflammatory responses. Contextually, important role of Th17 pathway has been demonstrated in patients with major psychosis. Currently, it is not adequately known whether Th17 pathway is crucially involved in the development of psychosis in patients with PD.

Method: PD patients (n=52) fulfilling the UK-PDS Brain Bank criteria and healthy subjects (n=14) were recruited during 2019-2022. Among the patients, 18 PD patients had psychosis, and their diagnosis was established by DSM-V. A panel of five critical Th17 pathway-related cytokines, such as IL-1β, IL-6, IL-17A, IL-23 and TNF-α were assayed in the plasma samples of all the PD patients and healthy controls using Bio-Plex kits in a Multiplex Suspension Array Platform. The plasma levels of the inflammatory cytokines were then correlated with various clinical features of PD patients.

Results: PD patients with psychosis had a significantly higher duration of illness in comparison to patients without psychosis. Besides, PD patients with psychosis had severe motor symptoms compared to PD patients without psychosis. Among the cytokines, only plasma levels of TNF-α were significantly different between PD patients without psychosis and healthy controls (p=0.05). Interestingly, age of onset in PD patients with psychosis correlated negatively with plasma levels of IL-23(p=0.05) and positively with TNF-α (p=0.05). In addition, plasma TNF-α levels also showed negative correlation with duration of illness in PD patients with psychosis (p=0.05); reduced TNF-α levels correlated with increased duration of the illness.

Conclusion: This preliminary study suggests important implications of Th17 pathway-related inflammatory cytokines in PD. The present findings for the first time demonstrate a pivotal role of Th17 pathway in PD patients with psychosis.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impact-of-th17-pathway-related-immuno-inflammatory-cytokines-in-the-risk-and-severity-of-parkinsons-disease/