Oxidative Modification and Its Implications for the Neurodegeneration of Parkinson's Disease.

Parkinson's disease (PD) is the second most common neurodegenerative disease. The major characteristics of PD include the loss of dopaminergic neurons in the substantia nigra and Lewy body depositions. Genetic defects, environment toxicants, and aging have been recognized as risk factors for the development of PD. Currently, although the pathogenesis of PD is still obscure, overwhelming evidence demonstrates that oxidative stress plays a central role in the progress of PD. Reactive oxygen species (ROS) function mainly through chemical reactions with atomic targets that lead to covalent oxidative modifications. Through the oxidative modification of ions, amino acids, amines, and nucleic acids, ROS exert augmented effects on the structures and functions of multiple macromolecules. These oxidative modifications can affect nucleic acid stability by oxidizing RNA, increasing mitochondrial DNA (mtDNA) mutation, and launching translesion synthesis (TLS); disturb protein homeostasis by accelerating α-synuclein aggregation, parkin aggregation, and proteasome dissociation; modulate dopamine release by activating ATP-sensitive potassium channels (K) and inactivating neuronal nicotinic acetylcholine receptors (nAChRs); and influence cellular self-defenses by promoting the cytoprotective effects of DJ-1 and PTEN-induced putative kinase 1 (PINK1) while inducing Akt dysregulation. Based on the above facts, we propose that various oxidative modifications may affect nucleic acid stability, protein homeostasis, the functionality of ion channels, and cellular self-defenses and that these processes lead to protein misfolding, dopamine depletion, and further neuronal death in PD.