title: Activation of type 5 metabotropic glutamate receptor promotes the proliferation of rat retinal progenitor cell via activation of the PI-3-K and MAPK signaling pathways.
abstract: The metabotropic glutamate receptor 5 (mGluR5) regulates neurogenesis in the brain, but the effect of mGluR5 on retinal progenitor cells (RPCs) remains unknown. In this study, we found that mGluR5 promoted the proliferation of rat RPCs with activation of the phosphatidylinositol-3-kinase (PI-3-K) and mitogen-activated protein kinase (MAPK) signaling pathways in vitro. The mGluR5 agonist (S)-3,5-dihydroxyphenylglycine hydrate (DHPG) increased the cellular viability in a concentration- and time-dependent manner, whereas the mGluR5 antagonist 6-methyl-2-(phenylethynyl)pyridine hydrochloride (MTEP) had the opposite effect, as shown by 3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine hydrochloride (MTT) assay. Treatment with DHPG (100 μM) also promoted the proliferation of RPCs, as indicated by 5-Bromo-2-deoxyUridine (BrdU) staining and flow cytometry, and likewise, MTEP (100 μM) and mGluR5 knockdown abolished the action of mGluR5 activity. Western blot demonstrated that the activation of mGluR5 enhanced the expression of Cyclin D1 and the phosphorylation level of PKC however, MTEP or mGluR5 knockdown also abrogated the effect of DHPG on RPCs. Furthermore, we found that activation of the extracellular signal-regulated protein kinase (ERK) and protein kinase B (AKT) signaling pathways was involved in the proliferation of RPC. After DHPG treatment, the levels of both p-ERK1/2 and p-AKT increased in a time-dependent manner. Then we used MTEP, mGluR5 knockdown, the ERK1/2 inhibitor U0126 and the AKT inhibitor LY294002 to pretreat the cells, and all of them clearly eliminated the influence of DHPG. These results demonstrated that mGluR5 regulates neurogenesis in RPCs through the MAPK and PI-3-K signaling pathways, and these findings may motivate a pharmacological study investigating a potential mechanism for the treatment of retinal diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD).
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China; Ningbo Medical Treatment Center Lihuili Hospital, Ningbo, Zhejiang 315040, China.
authors.forename: F
authors.initials: F
authors.lastname: Hu
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China.
authors.forename: B
authors.initials: B
authors.lastname: Ma
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China.
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China.
authors.forename: K
authors.initials: K
authors.lastname: Zhu
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China.
authors.forename: T
authors.initials: T
authors.lastname: Wei
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Xing
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China.
authors.forename: H
authors.initials: H
authors.lastname: Lu
authors.affiliation: Institute of Neurobiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China. Electronic address: liuy5599@mail.xjtu.edu.cn.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China. Electronic address: kangqy@mail.xjtu.edu.cn.
authors.forename: Q
authors.initials: Q
authors.lastname: Kang
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D058953:Neural Stem Cells / Q000187:drug effects / Q000378:metabolism*; D055495:Neurogenesis / Q000187:drug effects / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000187:drug effects / Q000378:metabolism*
chemical_list: C578937:Grm5 protein, rat; D064529:Receptor, Metabotropic Glutamate 5; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: metabotropic glutamate receptor 5; mitogen-activated protein kinases; phosphatidylinositol-3-kinase; proliferation; retinal progenitor cells