Neuronal NOS and cyclooxygenase-2 contribute to DNA damage in a mouse model of Parkinson’s disease

摘要

DNA damage is a proposed pathogenic factor in neurodegenerative disorders such as Parkinson’s disease. To probe the underpinning mechanism of such neuronal perturbation, we sought to produce an experimental model of DNA damage. We thus first assessed by in situ nick translation and emulsion autoradiography in the mouse brain the effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 4 × 20mg/kg, i.p., every 2 hours), a neurotoxin known to produce a model of Parkinson’s disease, on DNA. Here we show that DNA strand breaks occur in vivo in this mouse model of Parkinson’s disease with kinetics and a topography that parallel the degeneration of substantia nigra neurons, as assessed by FluoroJade-labeling. Previously, nitric oxide synthase (NOS) and cyclooxygenase-2 (Cox-2) were found to modulate MPTP-induced dopaminergic neuronal death. We thus assessed the contribution of these enzymes to DNA damage in mice lacking either neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), or Cox-2. We found that the lack of Cox-2 and of nNOS, but not of iNOS activity, attenuate MPTP-related DNA damage. We also found that not only nuclear, but mitochondrial DNA as well is a target for the MPTP insult. These results suggest that the loss of genomic integrity can be triggered by the concerted actions of nNOS and Cox-2, and provide further support to the view that DNA damage may contribute to the neurodegenerative process in PD.