Protective effect of melatonin against the 1-methyl-4-phenylpyridinium-induced inhibition of Complex I of the mitochondrial respiratory chain

In the present study, a novel property of melatonin is shown: a protective effect of melatonin on the respiratory chain in isolated rat liver mitochon dria and in striatal synaptosomes treated with 1-methyl-4-phenylpyridinium ion (MPP+). The cellular damage caused by MPP+, a compound that produces a Parkinsonian-like syndrome in humans, is the result of the mitochondrial re spiration inhibition at the Complex I level and oxidative stress induction. Treatment of mitochondria with MPP+ inhibits the respiration rate. This ef fect was prevented by the inclusion of melatonin in the incubation mixture. This preventive effect, which is not related to the antioxidative properti es of melatonin, seems to be due to the fact that melatonin prevents MPP+ i nteraction with Complex I. These results suggest that melatonin may protect against the effect of several Parkinsonogenic compounds that are associate d with progressive impairment of mitochondrial function and increased oxida tive damage.