Redox reactions of neurotransmitters possibly involved in the progression of Parkinson's Disease

In Parkinson's Disease the neuromelanin in the substania nigra is known to contain considerably increased amounts of iron suggesting the presence of f ree, unprotected iron ions during its formation. Iron(II) is known to inter act with peroxide via Fenton's reaction producing OH-radicals or ferryl (Fe (IV)) species. This can readily oxidize the neurotransmitter dopamine to th e neurotoxic 6-hydroxydopamine (6-OHDA) which is a strong reducing agent. T he produced 6-OHDA is, in turn, able to reduce and possibly release iron, a s iron(II), from the iron storage protein ferritin. This cycle of events co uld well explain the development of Parkinson's Disease due to a continuous production of cell damaging species. The contrasting behaviour of 6-OHDA w ith some other important catecholamines is discussed. (C) 2000 Elsevier Sci ence Inc. All rights reserved.