title: FGF9-induced changes in cellular redox status and HO-1 upregulation are FGFR-dependent and proceed through both ERK and AKT to induce CREB and Nrf2 activation.
abstract: Our previous studies demonstrated that fibroblast growth factor 9 (FGF9) protects cortical and dopaminergic neurons from 1-methyl-4-phenylpyridinium (MPP(+))-induced oxidative insult by upregulation of γ-glutamylcysteine synthetase (γ-GCS) and heme oxygenase-1 (HO-1). However, the mechanisms responsible for FGF9-induced γ-GCS and HO-1 upregulation remain uncharacterized. In the present study, we demonstrate the signaling pathways by which FGF9 upregulates HO-1 and γ-GCS expression. We found that FGF9-induced HO-1 and γ-GCS expression was prevented by PD173014, an inhibitor of the FGF receptor (FGFR). FGF9 treatment induced the phosphorylation of FGFR downstream signals of extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT in a dose- and time-dependent manner. The inhibition of MEK/ERK1/2 or PI3K/AKT activity by U0126 or wortmannin, but not the inhibition of phospholipase Cγ by U73122, prevented FGF9-induced γ-GCS and HO-1 upregulation, changes in cellular redox status, and neuroprotection against MPP(+) toxicity in primary cortical and dopaminergic neurons. Furthermore, FGF9 treatment enhanced the promoter activity of the cAMP-response element binding protein (CREB) and nuclear factor erythroid-derived 2-like 2 (Nrf2), and this phenomenon was blocked by PD173014 or U0126 or wortmannin. Knockdown of CREB and Nrf2 by shRNA blocked FGF9-induced γ-GCS and HO-1 upregulation, but not ERK and AKT phosphorylation. An in vivo study consistently showed that FGF9 overexpression using a lentivirus delivery system induced ERK1/2 phosphorylation and HO-1 upregulation and protected dopaminergic neurons against MPP(+) toxicity in rat substantia nigra. These results indicate that FGF9-induced HO-1 and γ-GCS upregulation is mediated by binding to FGFR and activation of two parallel downstream signaling pathways, ERK and AKT, which reconverge to induce CREB and Nrf2 transcriptional activity.
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan. Electronic address: jichuang@mail.ncku.edu.tw.
authors.forename: Jih-Ing
authors.initials: JI
authors.lastname: Chuang
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Jui-Yen
authors.initials: JY
authors.lastname: Huang
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Shaw-Jenq
authors.initials: SJ
authors.lastname: Tsai
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Insititute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: H Sunny
authors.initials: HS
authors.lastname: Sun
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Shang-Hsun
authors.initials: SH
authors.lastname: Yang
authors.affiliation: Department of Medical Research, Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Pei-Chin
authors.initials: PC
authors.lastname: Chuang
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Bu-Miin
authors.initials: BM
authors.lastname: Huang
authors.affiliation: Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Cheng-Hsin
authors.initials: CH
authors.lastname: Ching
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics* / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D051525:Fibroblast Growth Factor 9 / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000235:genetics* / Q000378:metabolism; D018384:Oxidative Stress; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; C496461:Fgf9 protein, rat; D051525:Fibroblast Growth Factor 9; D051267:NF-E2-Related Factor 2; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D051547:Heme Oxygenase-1; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: AKT; CREB; ERK1/2; Fibroblast growth factor 9; Free radicals; Heme oxygenase-1; MPP(+); Nrf2; γ-Glutamylcysteine synthetase