title: Exposure of C. elegans eggs to a glyphosate-containing herbicide leads to abnormal neuronal morphology.
abstract: Recent data demonstrate that chronic exposure of Caenorhabditis elegans (C. elegans) to a high-use glyphosate-containing herbicide, Touchdown (TD), potentially damages the adult nervous system. It is unknown, however, whether unhatched worms exposed to TD during the egg stage show abnormal neurodevelopment post-hatching. Therefore, we investigated whether early treatment with TD leads to aberrant neuronal or neurite development in C. elegans. Studies were completed in three different worm strains with green fluorescent protein (GFP)-tagged neurons to facilitate visual neuronal assessment. Initially, eggs from C. elegans with all neurons tagged with GFP were chronically exposed to TD. Visual inspection suggested decreased neurite projections associated with ventral nerve cord neurons. Data analysis showed a statistically significant decrease in overall green pixel numbers at the fourth larval (L4) stage (*p<0.05). We further investigated whether specific neuronal populations were preferentially vulnerable to TD by treating eggs from worms that had all dopaminergic (DAergic) or γ-aminobutyric acid (GABAergic) neurons tagged with GFP. As before, green pixel number associated with these discrete neuronal populations was analyzed at multiple larval stages. Data analysis indicated statistically significant decreases in pixel number associated with DAergic, but not GABAergic, neurons (***p<0.001) at all larval stages. Finally, statistically significant decreases (at the first larval stage, L1) or increases (at the fourth larval stage, L4) in superoxide levels, a developmental signaling molecule, were detected (*p<0.05). These data suggest that early exposure to TD may impair neuronal development, perhaps through superoxide perturbation. Since toxic insults during development may late render individuals more vulnerable to neurodegenerative diseases in adulthood, these studies provide some of the first evidence in this model organism that early exposure to TD may adversely affect the developing nervous system.
authors.affiliation: King University, Department of Biology, 1350 King College Road, Bristol, TN 37620, USA; Liberty University College of Osteopathic Medicine, 306 Liberty View Lane, Lynchburg, VA 24502, USA. Electronic address: kamcvey@liberty.edu.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: McVey
authors.affiliation: King University, Department of Biology, 1350 King College Road, Bristol, TN 37620, USA; Medical University of South Carolina, Physician Assistant Studies, 151B Rutledge Avenue, Charleston, SC 29425, USA. Electronic address: snapp@musc.edu.
authors.forename: Isaac B
authors.initials: IB
authors.lastname: Snapp
authors.affiliation: King University, Department of Biology, 1350 King College Road, Bristol, TN 37620, USA; Lincoln Memorial University, Debusk College of Osteopathic Medicine, 6965 Cumberland Gap Parkway, Harrogate, TN 37752, USA. Electronic address: megan.johnson02@lmunet.edu.
authors.forename: Megan B
authors.initials: MB
authors.lastname: Johnson
authors.affiliation: King University, Department of Biology, 1350 King College Road, Bristol, TN 37620, USA; The University of Tennessee Institute of Agriculture, Department of Animal Science, 366 Brehm Animal Science Building, 2506 River Drive, Knoxville, TN 37996, USA. Electronic address: rnegga@utk.edu.
authors.forename: Rekek
authors.initials: R
authors.lastname: Negga
authors.affiliation: King University, Department of Biology, 1350 King College Road, Bristol, TN 37620, USA. Electronic address: adpressley@outlook.com.
authors.forename: Aireal S
authors.initials: AS
authors.lastname: Pressley
authors.affiliation: King University, Department of Biology, 1350 King College Road, Bristol, TN 37620, USA. Electronic address: vafitsan@king.edu.
authors.forename: Vanessa A
authors.initials: VA
authors.lastname: Fitsanakis
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives* / Q000633:toxicity; D006540:Herbicides / Q000633:toxicity*; D009410:Nerve Degeneration / Q000139:chemically induced; D016501:Neurites / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000473:pathology*; D009943:Organophosphorus Compounds / Q000633:toxicity; D010063:Ovum / Q000187:drug effects* / Q000254:growth & development*; D013481:Superoxides / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D006540:Herbicides; C404484:N-(phosphonomethyl)glycine trimethylsulfonium salt; D009943:Organophosphorus Compounds; D013481:Superoxides; D005998:Glycine
keywords: C. elegans strain BZ555; C. elegans strain EG1285; DAergic neurons; Glyphosate-containing herbicides; Neurodevelopment; Touchdown