miR‐221 and Parkinson's disease: A biomarker with therapeutic potential.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, leading to various motor and non‐motor symptoms. Several cellular and molecular mechanisms such as alpha‐synuclein (α‐syn) accumulation, mitochondrial dysfunction, oxidative stress and neuroinflammation are involved in the pathogenesis of this disease. MicroRNAs (miRNAs) play important roles in post‐transcriptional gene regulation. They are typically about 21–25 nucleotides in length and are involved in the regulation of gene expression by binding to the messenger RNA (mRNA) molecules. miRNAs like miR‐221 play important roles in various biological processes, including development, cell proliferation, differentiation and apoptosis. miR‐221 promotes neuronal survival against oxidative stress and neurite outgrowth and neuronal differentiation. Additionally, the role of miR‐221 in PD has been investigated in several studies. According to the results of these studies, (1) miR‐221 protects PC12 cells against oxidative stress induced by 6‐hydroxydopamine; (2) miR‐221 prevents Bax/caspase‐3 signalling activation by stopping Bim; (3) miR‐221 has moderate predictive power for PD; (4) miR‐221 directly targets PTEN, and PTEN over‐expression eliminates the protective action of miR‐221 on p‐AKT expression in PC12 cells; and (5) miRNA‐221 controls cell viability and apoptosis by manipulating the Akt signalling pathway in PD. This review study suggested that miR‐221 has the potential to be used as a clinical biomarker for PD diagnosis and stage assignment. [ABSTRACT FROM AUTHOR]