The identification of mechanisms associated with Parkinson disease (PD) development in cognitive functioning would be of great usefulness to clarify PD pathogenesis and to develop preventive and therapeutic strategies. In this study, blood serum extracellular vesicle (EV) levels of the candidate microRNAs (small noncoding RNAs that play a role in gene expression regulation):,miR-7, miR-21, miR-153, miR-155, miR-200a and miR-214, have been investigated for association with PD in a group of 93 patients with cognitive parameters, PD symptoms, affected quality of life and some clinical characteristics. MiRNA was extracted from patients’ blood serum EVs, transcribed into cDNA and their expression was evaluated using RT-PCR. The miR-153 and miR-200a showed the most plausible correlations with cognitive functioning parameters such as general intellectual functioning, psychomotor speed, mental flexibility, and nonverbal executive functions. Moreover, lower levels of miR-153 were associated with attention span, working memory and psychomotor speed with learning. Increased levels of miR-200a, miR-7, miR-214, and miR-155 were also linked with neurological functioning, such as bradykinesia, tremor, balance and others. Despite the fact that due to small sample size, our results should be considered as preliminary, our study suggests that miRNA expression in EVs could be associated with symptom severity, cognitive impairment and quality of life in PD.

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and non‐motor symptoms, including cognitive decline and reduced quality of life. Identifying reliable biomarkers for disease progression and symptom severity remains a critical challenge. In this study, levels of oxidative stress–related microRNAs (miR‐24‐3p, miR‐103a‐3p, miR‐320a‐3p, miR‐494‐3p, miR‐126‐5p, and miR‐543) within blood serum extracellular vesicles (EVs) were examined in a cohort of 93 PD patients to assess their associations with cognitive function, symptom severity, quality of life, and other clinical characteristics. The methods included microRNA extraction from blood serum EVs, followed by cDNA synthesis and RT‐qPCR for expression analysis. Upregulation of miR‐126‐5p, as well as downregulation of miR‐24‐3p showed the strongest associations with symptom severity and cognitive decline, whereas downregulated miR‐320a‐3p levels correlated with patient‐reported quality of life in PD patients. Downregulation of miR‐103a‐3p, and miR‐543 expression showed slight associations with motor symptoms, cognitive function, and quality of life domains; however, some of these associations lacked statistical power. These findings indicate that specific microRNA expression profiles in extracellular vesicles are associated with PD symptom severity and progression, supporting their further evaluation as biomarkers in larger independent cohorts. image