title: Anti-Apoptotic Effect of IGF1 on Schwann Exposed to Hyperglycemia is Mediated by Neuritin, a Novel Neurotrophic Factor.
abstract: The aim of the present study is to explore the effects of exogenous insulin-like growth factor-1 (IGF1) on hyperglycemia-induced apoptosis of Schwann cells via neuritin-mediated pathway. Neuritin was identified with immunohistochemistry. Exogenous IGF1 was used to prevent possible changes in neuritin expression and apoptosis of Schwann cells isolated from rat sciatic nerves and cultured in high-glucose media. Neuritin silencing or overexpressing lentivirus transfection of Schwann cells was conducted. Expressions of neuritin at levels of transcription or translation were measured using quantitative PCR or Western blot. Caspase-3 and caspase-9 fluorometric assays were performed. Bcl-2 and Bax were assayed using Western blotting. Apoptosis of Schwann cells was measured using FACS analysis and TUNEL assay. A pathway of IGF1 action in relation to neuritin was explored. Neuritin and Bcl-2 protein were localized in Schwann cells of rats' sciatic nerves. In vitro, apoptosis increased with downregulated neuritin expression, which was prevented by exogenous IGF1 treatment in contrast to without, in Schwann cells isolated from rat sciatic nerve and cultured in high-glucose and serum-free media. A phosphatidylinositol-3-kinase (PI3K) inhibitor treatment blocked the action of IGF1. The inhibitor did not affect the apoptosis rate that decreased obviously after neuritin was overexpressed in Schwann cells. The apoptosis rate increased drastically after neuritin was silenced, and the resultant apoptosis was suppressed by a caspase inhibitor treatment but not affected by exogenous IGF1. The activities of caspase-3 and caspase-9 changed positively with apoptosis. An anti-apoptotic protein (Bcl-2) not Bax increased or decreased in neuritin-overexpressed or neuritin-silenced Schwann cells, respectively. Bcl-2-selective inhibitor blocked the anti-apoptotic effect of neuritin. IGF1 or neuritin was not found to affect glucose levels in media during the experiment. The anti-apoptotic effect of IGF1 on Schwann cells inflicted by hyperglycemia is mediated at least by neuritin, a novel neurotrophic factor, through PI3K and Bcl-2.
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Lingfei
authors.initials: L
authors.lastname: Yan
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Min
authors.initials: M
authors.lastname: Xie
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: He
authors.initials: H
authors.lastname: Lu
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Hongman
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Min
authors.initials: M
authors.lastname: Shi
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Yingduan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Chunhong
authors.initials: C
authors.lastname: Xi
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China. ljbzjlx18@aliyun.com.|Diabetic Neuropathy Study Group of Chinese Diabetes Society, 42 Dongsi Xidajie, Beijing, China. ljbzjlx18@aliyun.com.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Li
authors.affiliation: Endocrinology and Metabolism Department, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing, 210029, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D058851:GPI-Linked Proteins / Q000378:metabolism; D006943:Hyperglycemia / Q000473:pathology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D009479:Neuropeptides / Q000378:metabolism*; D010084:Oxidation-Reduction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000378:metabolism* / Q000473:pathology*; D012584:Sciatic Nerve / Q000378:metabolism
chemical_list: D058851:GPI-Linked Proteins; D009479:Neuropeptides; C105161:Nrn1 protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D007334:Insulin-Like Growth Factor I; D020169:Caspases
keywords: Hyperglycemia; IGF1; Neuritin expression; Schwann cell survival