title: Neuroprotective effect of ghrelin in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease by blocking microglial activation.
abstract: Ghrelin is an endogenous ligand for growth hormone (GH) secretagogue receptor 1a (GHS-R1a) and is produced and released mainly from the stomach. It was recently demonstrated that ghrelin can function as a neuroprotective factor by inhibiting apoptotic pathways. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes nigrostriatal dopaminergic neurotoxicity in rodents; previous studies suggest that activated microglia actively participate in the pathogenesis of Parkinson's disease (PD) neurodegeneration. However, the role of microglia in the neuroprotective properties of ghrelin is still unknown. Here we show that, in the mouse MPTP PD model generated by an acute regimen of MPTP administration, systemic administration of ghrelin significantly attenuates the loss of substantia nigra pars compacta (SNpc) neurons and the striatal dopaminergic fibers through the activation of GHS-R1a. We also found that ghrelin reduced nitrotyrosine levels and improved the impairment of rota-rod performance. Ghrelin prevents MPTP-induced microglial activation in the SNpc and striatum, the expression of pro-inflammatory molecules tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta), and the activation of inducible nitric oxide synthase. The inhibitory effect of ghrelin on the activation of microglia appears to be indirect by suppressing matrix metalloproteinase-3 (MMP-3) expression in stressed dopaminergic neurons because GHS-R1a is not expressed in SNpc microglial cells. Finally, in vitro administration of ghrelin prevented 1-methyl-4-phenylpyridinium-induced dopaminergic cell loss, MMP-3 expression, microglial activation, and the subsequent release of TNF-alpha, IL-1beta, and nitrite in mesencephalic cultures. Our data indicate that ghrelin may act as a survival factor for dopaminergic neurons by functioning as a microglia-deactivating factor and suggest that ghrelin may be a valuable therapeutic agent for neurodegenerative diseases such as PD.
authors.affiliation: Department of Pharmacology and Medical Research Center for Bioreaction to ROS and Biomedical Science Institute, Kyunghee University School of Medicine, Seoul, 130-701, Korea.
authors.forename: Minho
authors.initials: M
authors.lastname: Moon
authors.forename: Hyo Geun
authors.initials: HG
authors.lastname: Kim
authors.forename: Lakkyong
authors.initials: L
authors.lastname: Hwang
authors.forename: Ji-Hyung
authors.initials: JH
authors.lastname: Seo
authors.forename: Sehee
authors.initials: S
authors.lastname: Kim
authors.forename: Sunyoung
authors.initials: S
authors.lastname: Hwang
authors.forename: Soonyong
authors.initials: S
authors.lastname: Kim
authors.forename: Dahm
authors.initials: D
authors.lastname: Lee
authors.forename: Hyunju
authors.initials: H
authors.lastname: Chung
authors.forename: Myung Sook
authors.initials: MS
authors.lastname: Oh
authors.forename: Kyung-Tae
authors.initials: KT
authors.lastname: Lee
authors.forename: Seungjoon
authors.initials: S
authors.lastname: Park
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000378:metabolism / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000378:metabolism; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D005786:Gene Expression Regulation / Q000187:drug effects; D054439:Ghrelin / Q000494:pharmacology*; D005911:Gliosis / Q000139:chemically induced / Q000517:prevention & control; D053583:Interleukin-1beta / Q000378:metabolism; D020267:MPTP Poisoning / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D008636:Mesencephalon / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects*; D009043:Motor Activity / Q000187:drug effects; D009410:Nerve Degeneration / Q000139:chemically induced / Q000517:prevention & control; D009474:Neurons / Q000187:drug effects; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009573:Nitrites / Q000378:metabolism; D051381:Rats; D054440:Receptors, Ghrelin / Q000235:genetics / Q000378:metabolism; D053719:Tandem Mass Spectrometry / Q000379:methods; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
chemical_list: D054439:Ghrelin; D053583:Interleukin-1beta; D018696:Neuroprotective Agents; D009573:Nitrites; D054440:Receptors, Ghrelin; D014409:Tumor Necrosis Factor-alpha; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D014446:Tyrosine 3-Monooxygenase; D019278:Matrix Metalloproteinase 3; D004298:Dopamine