Background: Protective effect of roscovitine and deregulation of the p-RB/E2F1 have not been well studied in PD models generated by repeated oral administration of rotenone.
Objective: These experiments evaluated the effects of repeated oral gavage of rotenone on the activation of p-RB/E2F1 and the effects of roscovitine on the regulation of dopaminergic neuronal injury and the behavior of PD in mice.
Methods: Using 2.5% carboxymethylcellulose and 1.25% chloroform as a vehicle solution, rotenone (30 mg/kg) was administered via oral gavage once daily for 30 days in C57 mice. Behavioral profiles (pole test and traction test) were assessed in these PD models, and oxidative stress levels were evaluated in the midbrain. The immunoreactivities of TH, α-synuclein (α-syn), p-RB, E2F1 and cleaved caspase-3 in the substantia nigra were examined with a laser confocal microscope. Pharmacological inhibition of cyclin-dependent kinase with roscovitine was achieved by intraperitoneal (IP) injection at a dose of 50 mg/kg daily.
Results: All rotenone-administered C57 mice showed the typical behavioral features of PD: stiffness, bradykinesia, or hypokinesia. Behavioral testing with the pole test and traction test indicated that the rotenone group, but not the vehicle group, was affected. Spectrophotometric analysis demonstrated that glutathione (GSH) and superoxide dismutase (SOD) activity was decreased, and the generation of malondialdehyde (MDA) was elevated in the midbrain of the rotenone-treated group. After oral administration of rotenone, a loss of nigral tyrosine hydroxylase (TH)-positive neurons was observed. The immune response of α-syn was enhanced in the cytoplasm of dopaminergic neurons from the rotenone-induced neurotoxicity. Rb phosphorylation at serine 780, which affected Rb binding to E2F, was induced after rotenone treatment. The activation of E2F1, which is involved in the regulation of the cell cycle, was also induced from chronic exposure to rotenone. Moreover, administration of the cell cycle inhibitor roscovitine protected against rotenone-induced nigral dopaminergic neuronal injury and inhibited cleaved caspase-3 activation. Roscovitine also markedly ameliorated the behavior of PD mice.
Conclusions: Mouse models of Parkinson's disease were established by oral rotenone administration and reproduced some of the features of dopaminergic neuronal degeneration. Roscovitine protects against rotenone-induced parkinsonism.
Keywords: E2F1; Parkinson’s disease (PD); Roscovitine; cell cycle; dopaminergic neuron; p-RB; rotenone.