title: Weight of evidence evaluation of a network of adverse outcome pathways linking activation of the nicotinic acetylcholine receptor in honey bees to colony death.
abstract: Ongoing honey bee (Apis mellifera) colony losses are of significant international concern because of the essential role these insects play in pollinating crops. Both chemical and non-chemical stressors have been implicated as possible contributors to colony failure; however, the potential role(s) of commonly-used neonicotinoid insecticides has emerged as particularly concerning. Neonicotinoids act on the nicotinic acetylcholine receptors (nAChRs) in the central nervous system to eliminate pest insects. However, mounting evidence indicates that neonicotinoids also may adversely affect beneficial pollinators, such as the honey bee, via impairments on learning and memory, and ultimately foraging success. The specific mechanisms linking activation of the nAChR to adverse effects on learning and memory are uncertain. Additionally, clear connections between observed impacts on individual bees and colony level effects are lacking. The objective of this review was to develop adverse outcome pathways (AOPs) as a means to evaluate the biological plausibility and empirical evidence supporting (or refuting) the linkage between activation of the physiological target site, the nAChR, and colony level consequences. Potential for exposure was not a consideration in AOP development and therefore this effort should not be considered a risk assessment. Nonetheless, development of the AOPs described herein has led to the identification of research gaps which, for example, may be of high priority in understanding how perturbation of pathways involved in neurotransmission can adversely affect normal colony functions, causing colony instability and subsequent bee population failure. A putative AOP network was developed, laying the foundation for further insights as to the role of combined chemical and non-chemical stressors in impacting bee populations. Insights gained from the AOP network assembly, which more realistically represents multi-stressor impacts on honey bee colonies, are promising toward understanding common sensitive nodes in key biological pathways and identifying where mitigation strategies may be focused to reduce colony losses.
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA. Electronic address: LaLone.Carlie@epa.gov.
authors.forename: Carlie A
authors.initials: CA
authors.lastname: LaLone
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Villeneuve
authors.affiliation: University of Nebraska-Lincoln, Department of Entomology, 105A Entomology Hall, Lincoln, NE 68583, USA.
authors.forename: Judy
authors.initials: J
authors.lastname: Wu-Smart
authors.affiliation: ORISE Research Participation Program, U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA.
authors.forename: Rebecca Y
authors.initials: RY
authors.lastname: Milsk
authors.affiliation: U.S. Environmental Protection Agency, Office of Pesticide Programs, Washington D.C. 20460, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Sappington
authors.affiliation: U.S. Environmental Protection Agency, Office of Pesticide Programs, Washington D.C. 20460, USA.
authors.forename: Kristina V
authors.initials: KV
authors.lastname: Garber
authors.affiliation: U.S. Environmental Protection Agency, Office of Pesticide Programs, Washington D.C. 20460, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Housenger
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA.
authors.forename: Gerald T
authors.initials: GT
authors.lastname: Ankley
mesh_terms: D000073931:Adverse Outcome Pathways; D000818:Animals; D001516:Bees; D007306:Insecticides / Q000009:adverse effects*; D000073943:Neonicotinoids / Q000009:adverse effects*; D011978:Receptors, Nicotinic / Q000502:physiology*
chemical_list: D007306:Insecticides; D000073943:Neonicotinoids; D011978:Receptors, Nicotinic
keywords: Adverse outcome pathway; Colony loss; Honey bee; Neonicotinoids; Network; Nicotinic acetylcholine receptor activation