Peroxynitrite induced formation of the neurotoxins 5-S-cysteinyl-dopamine and DHBT-1: Implications for Parkinson’s disease and protection by polyphenols

Mechanisms of nigral cell injury in Parkinson’s disease remain unclear, although a combination of increased oxidative stress, the formation of catecholamine–quinones and the subsequent formation of neurotoxic cysteinyl–catecholamine conjugates may contribute. In the present study, peroxynitrite was observed to generate both 2-S- and 5-S-cysteinyl-dopamine and a dihydrobenzothiazine species, DHBT-1, following the reaction of dopamine with l-cysteine. The formation of 5-S-cysteinyl-dopamine and DHBT-1 in the presence of peroxynitrite induced significant neuronal injury. Pre-treatment of cortical neurons with pelargonidin, quercetin, hesperetin, caffeic acid, the 4′-O-Me derivatives of catechin and epicatechin (0.1–3.0 μM) resulted in concentration dependant protection against 5-S-cysteinyl-dopamine-induced neurotoxicity. These data suggest that polyphenols may protect against neuronal injury induced by endogenous neurotoxins relevant to the aetiology of the Parkinson disease.