L-dopa related hyperhomocysteinemia: A possible mediator of toxicity?

L-dopa is the most effective drug in the symptomatic management of PD and extends the life span of PD patients.The question whether L-dopa is neurotoxic remains however unresolved. In recent years, increased Homocysteine (Hcy) levels have been observed in L-dopa treated Parkinson's disease (PD) patients, resulting from L-dopa O-methylation by the enzyme catechol-O-methyltransferase. This review summarizes current evidences supporting the possible role of Hcy as mediator of L-dopa toxicity mainly on dopaminergic neurons