Neuroprotective Effects of Antidepressants via Upregulation of Neurotrophic Factors in the MPTP Model of Parkinson's Disease.

Abstract

Neurotrophic factors are essential for neuronal survival, plasticity, and development and have been implicated in the action mechanism of antidepressants. In this study, we assessed the neurotrophic factor-inducing and neuroprotective properties of antidepressants. In the first part of the study, we found that fluoxetine, imipramine, and milnacipran (i.p., 20mg/kg/day for 1week or 3weeks) upregulated brain-derived neurotrophic factor in the striatum and substantia nigra both at 1week and 3weeks. In contrast, an increase in the glial-derived neurotrophic factor was more obvious at 3weeks after the antidepressants treatment. Specifically, it was found that fluoxetine and imipramine are more potent in raising the levels of neurotrophic factors than milnacipran. Furthermore, antidepressants elevated the phosphorylation of extracellular signal-regulated-protein kinase (ERK1/2) and the serine/threonine kinase Akt. In the second part of the study, we compared the neuroprotective effects of fluoxetine, imipramine, and milnacipran in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease. Pretreament with fluoxetine, imipramine or milnacipran for 3weeks reduced MPTP-induced dopaminergic neurodegeneration and microglial activation in the nigrostriatal pathway. Neurochemical analysis by HPLC exhibited that antidepressants attenuated the depletion of striatal dopamine. In consistent, beam test showed that behavioral impairment was ameliorated by antidepressants. Neuroprotective effects were more prominent in the fluoxetine or imipramine treatment group than in milnacipran treatment group. Finally, we found that neuroprotection of the antidepressants against 1-methyl-4-phenylpyridinium neurotoxicity in SH-SY5Y cells was attenuated by ERK or Akt inhibitor. These results indicate that neuroprotection by antidepressants might be associated with the induction of neurotrophic factors, and antidepressant could be a potential therapeutic intervention for treatment of Parkinson's disease.