title: Inhibition of neurite outgrowth and alteration of cytoskeletal gene expression by sodium arsenite.
abstract: Arsenic compounds that are often found in drinking water increase the risk of developmental brain disorders. In this study, we performed live imaging analyses of Neuro-2a cells expressing SCAT3, a caspase-3 cleavage peptide sequence linking two fluorescent proteins; enhanced cyan fluorescence protein (ECFP) and Venus, to determine whether sodium arsenite (NaAsO(2); 0, 1, 5, or 10 μM) affects both neurite outgrowth and/or induces apoptosis with the same doses and in the same cell cultures. We observed that the area ratio of neurite to cell body in SCAT3-expressing cells was significantly reduced by 5 and 10 μM NaAsO(2), but not by 1 μM, although the emission ratio of ECFP to Venus, an endpoint of caspase-3 activity, was not changed. However, cytological assay using apoptotic and necrotic markers resulted in that apoptosis, but not necrosis, was significantly induced in Neuro-2a cells when NaAsO(2) exposure continued after the significant effects of NaAsO(2) on neurite outgrowth were found by live imaging. These results suggested that neurite outgrowth was suppressed by NaAsO(2) prior to NaAsO(2)-induced apoptosis. Next, we examined the effects of NaAsO(2) on cytoskeletal gene expression in Neuro-2a cells. NaAsO(2) increased the mRNA levels of the light and medium subunits of neurofilament and decreased the mRNA levels of tau and tubulin in a dose-dependent manner; no significant effect was found in the mRNA levels of the heavy subunit of neurofilament, microtubule-associated protein 2, or actin. The changes in cytoskeletal gene expression are likely responsible for the inhibitory effects of NaAsO(2) on neurite outgrowth.
authors.affiliation: Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Kyaw Htet
authors.initials: KH
authors.lastname: Aung
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kurihara
authors.forename: Shizuka
authors.initials: S
authors.lastname: Nakashima
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Maekawa
authors.forename: Keiko
authors.initials: K
authors.lastname: Nohara
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Shinji
authors.initials: S
authors.lastname: Tsukahara
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D020261:Arsenic Poisoning / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D018053:Arsenites / Q000633:toxicity*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D048430:Cell Shape / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D031541:Fluorescence Resonance Energy Transfer; D005786:Gene Expression Regulation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009336:Necrosis; D016501:Neurites / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D016900:Neurofilament Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D017670:Sodium Compounds / Q000633:toxicity*; D013997:Time Factors; D059008:Time-Lapse Imaging; D014162:Transfection; D014404:Tubulin / Q000235:genetics / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D016875:tau Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D018053:Arsenites; D001426:Bacterial Proteins; D008164:Luminescent Proteins; C558298:Mapt protein, mouse; D008869:Microtubule-Associated Proteins; C079240:Mtap2 protein, mouse; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D017670:Sodium Compounds; D014404:Tubulin; D014874:Water Pollutants, Chemical; C527701:enhanced cyan fluorescent protein; D016875:tau Proteins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; C017947:sodium arsenite