Potential Roles of MicroRNAs in Neurodegenerative Diseases

Neurodegenerative diseases are defined by advanced neuronal loss and can occur in hereditary or sporadic forms. As is generally known, the most common neurodegenerative diseases are Alzheimer's disease (AD) and Parkinson's disease (PD). Among these, AD is defined by the accumulation of beta-amyloid plaques, hyper phosphorylation of tau proteins, and chronic inflammation leading to neuronal loss. PD is related to the degeneration of dopaminergic neurons in the substantia nigra. Because of the wide heterogeneity of neurodegenerative diseases, various difficulties are encountered in diagnosing disease subtypes and developing effective treatment approaches. In recent years, microRNAs (miRNAs) have become efficient genetic biomarkers for several diseases. miRNAs regulate gene expressions post-transcriptionally and thus play a role in numerous neuronal and non-neuronal cell functions. Prior investigations have indicated the expression of miRNAs to become altered under pathological conditions, thereby suggesting that they may play a role in neurodegenerative diseases. This review focuses on the function of miRNAs in neurodegeneration and the possible contribution of altered levels of miRNAs and their target mRNAs in AD and PD patients compared to the controls shown in the previous studies. In short, altered expressions of miRNAs may play a role as potential diagnostic biomarkers with regard to neurodegenerative diseases.