Melatonin protects against MPTP/MPP+‐induced mitochondrial DNA oxidative damage in vivo and in vitro

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Abstract
The effects of melatonin on the mitochondrial DNA (mtDNA) damage induced by 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridine ion (MPP+) were investigated both in vivo and in vitro. MPTP (24 mg/kg, s.c.) induced a rapid increase in the immunoreactivity of 8-hydroxyguanine (8-oxoG), a common biomarker of DNA oxidative damage, in the cytoplasm of neurons in the Substantia Nigra Compact of mouse brain. Melatonin preinjection (7.5, 15 or 30 mg/kg, i.p.) dose-dependently prevented MPTP-induced DNA oxidative damage. In SH-SY5Y cells, MPP+ (1 mm) increased the immunoreactivity of 8-oxoG in the mitochondria at 1 hr and in the nucleus at 3 hr after treatment. Melatonin (200 μm) preincubation significantly attenuated MPP+-induced mtDNA oxidative damage. Furthermore, MPP+ time-dependently increased the accumulation of mitochondrial oxygen free radicals (mtOFR) from 1 to 24 hr and gradually decreased the mitochondrial membrane potential (Ψm) from 18 to 36 hr after incubation. At 72 hr after incubation, MPP+ caused cell death in 49% of the control. However, melatonin prevented MPP+-induced mtOFR generation and Ψm collapse, and later cell death. The present results suggest that cytoprotection of melatonin against MPTP/MPP+-induced cell death may be associated with the attenuation of mtDNA oxidative damage via inhibition of mtOFR generation and the prevention of Ψm collapse.

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