Peroxidation and Halogenation Stress: Windows to a Better Understanding of Sporadic Parkinson’s Disease

Oxidative stress is considered as an important pathogenic mechanism in Parkinson’s disease. Two types of oxidative stress, peroxidation and halogenation stress, are gaining increasing importance as biochemical windows to a better understanding of the pathogenesis of this disease. Peroxidation stress is due to excess of hydrogen peroxide, and it is related to the presence of many peroxidation-related molecular markers in Parkinsonian patients, and to misfolding of proteins. Peroxidation-induced misfolded proteins show altered functionality, such as loss of neuroprotective activity and tendency to form proteinaceous aggregates inside neurons. Peroxidation stress is also detected by a loss of activity of the main hydrogen peroxide scavengers in cerebrospinal fluid of patients. Altered hydrogen peroxide scavenging also leads to halogenation stress. Halogenation stress is characterized by the excess of halogenated molecules such as hypohalous acids, haloamines and halogenated proteins. Halogenated amines and proteins are thought to be deleterious for neurons, and they could play an important role in the etiology of Parkinson’s disease.