title: Carbamate nerve agent prophylatics exhibit distinct toxicological effects in the zebrafish embryo model.
abstract: Pyridostigmine bromide (PB) is an FDA-approved drug for the treatment of myasthenia gravis and a prophylactic pre-treatment for organophosphate nerve agent poisoning. Current methods for evaluating nerve agent treatments include enzymatic studies and mammalian models. Rapid whole animal screening tools for assessing the effects of nerve agent pre-treatment and post-exposure drugs represent an underdeveloped area of research. We used zebrafish as a model for acute and chronic developmental exposure to PB and two related carbamate acetylcholinesterase (AChE) inhibitors, neostigmine bromide (NB) and physostigmine (PS). Lethal doses and gross morphological phenotypes resulting from exposure to sub-lethal doses of these compounds were determined. Quantitative analyses of motility impairment and AChE enzyme inhibition were used to determine optimal dosing conditions for evaluation of the effects of carbamate exposures on neuronal development; ~50% impairment of response to startle stimuli and >50% inhibition of AChE activity were observed at 80 mMPB, 20 mM NB and 0.1 mM PS. PB induced stunted somite length, but no other phenotypic effects were observed. In contrast, NB and PS induced more severe phenotypic morphological defects than PB as well as neurite outgrowth mislocalization. Additionally, NB induced mislocalization of nicotinic acetylcholine receptors, resulting in impaired synapse formation. Taken together, these data suggest that altered patterns of neuronal connectivity contribute to the developmental neurotoxicity of carbamates and demonstrate the utility of the zebrafish model for distinguishing subtle structure-based differential effects of AChE inhibitors, which include nerve agents, pesticides and drugs.
authors.affiliation: Asymmetric Operations Department, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, United States; McKusick Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
authors.forename: Audrey
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Department of Cell & Developmental Biology, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, United States.
authors.forename: Marc
authors.initials: M
authors.lastname: Wolman
authors.affiliation: Department of Cell & Developmental Biology, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Granato
authors.affiliation: Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Parsons
authors.affiliation: McKusick Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States; Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: McCallion
authors.affiliation: Asymmetric Operations Department, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, United States.
authors.forename: Jody
authors.initials: J
authors.lastname: Proescher
authors.affiliation: Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, United States. Electronic address: emily.english@jhuapl.edu.
authors.forename: Emily
authors.initials: E
authors.lastname: English
mesh_terms: D000818:Animals; D002219:Carbamates / Q000633:toxicity*; D002800:Cholinesterase Inhibitors / Q000633:toxicity*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000187:drug effects; D009388:Neostigmine / Q000633:toxicity; D000067397:Nerve Agents / Q000633:toxicity*; D055495:Neurogenesis / Q000187:drug effects; D010830:Physostigmine / Q000633:toxicity; D011729:Pyridostigmine Bromide / Q000633:toxicity; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism
chemical_list: D002219:Carbamates; D002800:Cholinesterase Inhibitors; D000067397:Nerve Agents; D009388:Neostigmine; D010830:Physostigmine; D011729:Pyridostigmine Bromide
keywords: Acetylcholinesterase; Carbamate; Neostigmine bromide; Nerve agent treatment; Physostigmine; Pyridostigmine bromide