Recent advances in pharmacological therapy of Parkinson’s disease: Levodopa and carbidopa protective effects against DNA oxidative damage

Parkinson’s disease is one of the most common progressive neurodegenerative disorder. It is characterized by the depletion of dopamine in the dopaminergic neurons of the striatum of the brain. Pharmacological treatment involves the administration of a dopamine precursor, levodopa (L-Dopa), which crosses the blood-brain barrier and replaces the loss of dopamine in the brain. One of the main drawbacks of the administration of L-Dopa is its short half-life, due to the presence of enzymes, such as the amino acid decarboxylase (AADC), able to rapidly metabolize L-Dopa. For this reason the intake of L-Dopa takes always place together with an AADC inhibitor such as carbidopa. The assumption of carbidopa increases L-Dopa half-life, but several patients need to increase the dosage of the pharmacological therapy during the progression of the disease. Another area of dispute is represented by the possibility that L-Dopa can exert a toxic effect on the cells, both in peripheral and in central nervous system, increasing the production of ROS following its conversion to dopamine. Past studies reported toxic effects of L-Dopa in vitro and show conflicting data in in vivo experiments. More recent studies have however shown that L-dopa may exert a protective and antioxidant effect on dopaminergic cells, and its combination with carbidopa in pharmacological treatment amplifies antioxidant capability.