Proteomic and behavioral alterations following developmental emamectin benzoate exposure in rats – Effects in development and adulthood
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Proteomic and behavioral alterations following developmental emamectin benzoate exposure in rats – effects in development and adulthood
Emily M. Pitzer1, Tracey E. Beasley1, Garyn L. Jung1, Kathy L. McDaniel1, William T. Padgett1, Witold M. Winnik1, David W. Herr1
1Neurological and Endocrine Toxicology Branch, PHITD, CPHEA, ORD, US EPA, Research Triangle Park, NC
Early neurodevelopmental periods are vulnerable to environmental compounds. Unfortunately, there are few adverse outcome pathways (AOP) that explore these critical periods. AOPs detail a series of biological responses linked by key events following a molecular initiating event and ending in an adverse effect. We are using proteomic changes produced by xenobiotics that can occur during this susceptible period of development, to assess molecular alterations which can be applied in the AOP framework. Additionally, behavioral endpoints were assessed to understand potential adverse outcomes that may be related to our molecular observations. Pregnant Long Evans rats were gavaged with emamectin benzoate (EB; 3.78 mg/kg in 5 mL/kg DI water) or vehicle, from gestational day 6 to postnatal day (PND) 21. For proteomic experiments, pup regional brain tissues were collected throughout the postnatal period of exposure (PND2, 8, 15, 22); animals were perfused with phosphate buffered saline, dissected and the tissues stored at -80°C. Cortex samples were assessed for proteomic content using Orbitrap LC-MS and identified proteins were then further processed using Proteome Discover and Ingenuity Pathway Analysis software. Behaviors were assessed throughout the experimental period, starting during early postnatal days, assessed at weanling/juvenile timepoints, and into adulthood. Behavioral assays include pup righting (PND 2-7), a modified functional observational battery for pups and adults (PND 22, 41, and 63), locomotor activity in figure-eight mazes (PND 13, 17, 21, 29, and 64), novel object recognition (PND 34-37), acoustic startle response (PND 29 and PND 77), and the Morris water maze (PND 76-92). Proteomic analyses showed that protein signatures for EB-treated rats differed in the cortex by sex as well as by age. Analysis indicates alterations in proteins implicating presynaptic vesicle docking/fusion machinery, cell-cell adhesion receptors and proteins, or enzymes involved in transcription and/or translation regulation. Behaviorally we observed that EB-exposed offspring displayed altered ontogeny of locomotor activity at PND17, decreased startle response at PND 29, and had uncoordinated hindlimb movements which began in early postnatal weeks and persisted into adulthood. Additional proteomic analysis of other brain regions and inclusion of cognitive neurobehavioral tasks are on-going. Overall, we observe changes in proteomic signatures during developmental treatment with EB that differed across the postnatal period as well as displayed sex-related differences. Behavioral changes are present in EB rats, some of which are also observed in adulthood following developmental exposure. The protein level changes and observed apical behavioral endpoints could aid in AOP development. This is an abstract of a proposed presentation and does not necessarily reflect US EPA policy.