title: The peroxynitrite pathway in development: phenytoin and benzo[a]pyrene embryopathies in inducible nitric oxide synthase knockout mice.
abstract: Nitric oxide generated by nitric oxide synthases (NOSs) can react with reactive oxygen species (ROS), forming peroxynitrite, which may contribute to the ROS-initiated macromolecular damage implicated in the embryopathic effects of both endogenous and drug-enhanced oxidative stress. Inducible NOS (iNOS) is nonconstitutive in most tissues, and its embryonic expression and developmental importance are unknown. Herein, during organogenesis (Gestational Days 9 and 10), wild-type B6129PF2 embryos in culture were highly susceptible to the ROS-initiating teratogens phenytoin and benzo[a]pyrene, whereas iNOS knockout embryos were substantially but not completely protected (p < .05), implicating iNOS in the embryopathic mechanism. However, in contrast to prostaglandin H synthase-catalyzed teratogen bioactivation and ROS formation, which occurs within the embryo, in vivo iNOS expression was limited to placental tissue. These results suggest that the diffusion of nitric oxide from placental progenitor tissue (ectoplacental cone) to embryonic target tissues contributes to the embryopathic effects of ROS-initiating teratogens in embryo culture, which may constitute a mechanism by which embryonic determinants of ROS-mediated teratogenesis can be modulated by maternal extra-embryonic processes.
authors.affiliation: Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sonja
authors.initials: S
authors.lastname: Kasapinovic
authors.forename: Gordon P
authors.initials: GP
authors.lastname: McCallum
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wiley
authors.forename: Peter G
authors.initials: PG
authors.lastname: Wells
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D004622:Embryo, Mammalian / Q000187:drug effects; D005260:Female; D005315:Fetal Diseases / Q000139:chemically induced* / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D030421:Peroxynitrous Acid / Q000502:physiology*; D010672:Phenytoin / Q000633:toxicity*; D010920:Placenta / Q000187:drug effects / Q000201:enzymology; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013723:Teratogens / Q000633:toxicity
chemical_list: D017382:Reactive Oxygen Species; D013723:Teratogens; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D001564:Benzo(a)pyrene; D010672:Phenytoin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D011451:Prostaglandin-Endoperoxide Synthases