The Protective Effect Of Nesfatin-1on Dopaminergic Neurons And Its Underlying Mechanisms

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by progressive motor dysfunction. The key neuropathological features of PD are the loss of dopaminergic neurons in the substantia nigra (SN) and thus dopamine depletion in the striatum. However, the precise mechanisms leading to neurodegeneration in PD are not known, which genetic and environment factors are all involved. Up to now, there is no effective treatment for preventing or slowing the progression of neurodegeneration of dopaminergic neurons in the SN. Therefore, it is of great importance to investigate the etiology of PD and search for effective drugs to treat and prevent PD.Nesfatin-1, a newly discovered82-amino-acid neuropeptide released by X/A like endocrine cells in the gastric glands, regulates food intake, energy homeostasis, reproductive processes, stress response, cognition. It is also related to depression, anxiety, and epilepsy. The recent studies that it could display neuroprotective effects in subarachnoid hemorrhage and brain injury seem particularly intriguing. However, the protective effect of nesfatin-1on dopaminergic neurons has not been elucidated. In the present study,1-methyl-4-phenyl-1,2,3,6-tetrahydropyridi (MPTP)-treated mice and1-methyl-4-phenylpyridillium ion (MPP+)-treated MES23.5dopaminergic cells were selected as PD models to investigate the protective effect of nesfatin-1on dopaminergic neurons and to elucidate its underlying mechanisms. To investigate the effects of nesfatin-1on MPTP-induced toxicity in PD mice, the number of tyrosine hydroxylase (TH) positive neurons, TH levels in SN, dopamine and its metabolites contents, TH immunoreactive fibers in the striatum (Str) were tested by immunofluorescence, western blot, high-performance liquid chromatograph (HPLC), immunohistochemistry, respectively. Further studies were conducted to detect the effect of nesfatin-1on the changes of cell viability, the mitochondrial transmembrane potential (△ΨM), caspase-3levels and cytochrome c (Cyt C) release in MPP+-treated MES23.5cells. Nesfatin-1could induce the phosphorylation of extracellular regulated protein kinases (ERK1/2), which could be abolished by its inhibitor PD98059. The effects of nesfatin-1could not be abolished by PD98059. The results are as follows: 1. The contents of DA, DOPAC and HVA in MPTP-treated mice were observed decreased compared with control group (P<0.05). Pretreatment with nesfatin-1(100ng/μL and200ng/μL), it could antagonize MPTP-induced reduction in the contents of DA, DOPAC and HVA (P<0.05). In400ng/μL nesfatin-1pretreatment group, only DA and HVA contents could be observed increased (P <0.05).2. In MPTP-treated mice, reduction in the number of TH-positive neurons, TH protein levels in the SN and TH immunoreactive fibers in the Str were observed compared with that of control (P<0.05). Nesfatin-1(100ng/μL,200ng/μL and400ng/μL) pretreatment significantly abolished these effects (P<0.05).3. MPP+(300μmol/L) could induce the reduction in cell viability in MES23.5cells (P<0.01). Pre-incubated with nesfatin-1(10-13to10-7mol/L) could antagonize MPP+-induced reduction in cell viability.4. MPP+(300μmol/L) treatment resulted in△Ψm decrease assessed by flow cytometry after24h exposure in MES23.5cells. Pre-incubation with nesfatin-1(10-8and10-9mol/L) could abolish this effect.5. Cyt C levels were observed decreased in the mitochondrion and increased in the cytosol after MPP+treatment.10-9mol/L nesfatin-1pretreatment significant antagonized Cyt C release from the mitochondrion to cytosol induced by MPP+(P<0.05).6. MPP+(300μmol/L) treatment induced easpase-3activation. This effect could be abolished by nesfatin-1pretreatment (P<0.05).7. MPP+(300μmol/L) treatment could induce hypercondensed, broken and anachromasis of nuclei in MES23.5cells.10-9mol/L nesfatin-1pretreatment attenuated the morphological changes of these cells.8. Nesfatin-1could induced phosphorylation of ERK1/2which reached its peak at30min and could be abolished by ERK/MAPK inhibitors PD98059. PD98059(10μmol/L) could not abolish the effects of nesfatin-1on the decrease of△ΨM and caspase-3activation induced by MPP+.The results indicate that nesfatin-1has neuroprotective effect in PD models both in vivo and in vitro. The underlying mechanism might be related to prevent mitochondrion damage by inhibiting Cyt C release from mitochondrion and subsequent caspase3-mediated apoptosis cascades of cells. The anti-apoptotic action of nesfatin-1is independent of ERK1/2/MAPK pathway. This work provides new evidences to explore the possible use of nesfatin-1as a potential therapeutic drug in PD by its anti-apoptotic property.