Programmed Cell Death in the Honey Bee (Apis mellifera) (Hymenoptera: Apidae) Worker Brain Induced by Imidacloprid

• Published in: Journal of economic entomology 2015-08, Vol.108 (4), p.1486-1494
• Main Authors: Wu, Yan-Yan, Zhou, Ting, Wang, Qiang, Dai, Ping-Li, Xu, Shu-Fa, Jia, Hui-Ru, Wang, Xing
• Format: Article
• Language: English
• Subjects: adults; Animals; APICULTURE AND SOCIAL INSECTS; Apis mellifera; Apoptosis; Apoptosis - drug effects; Autophagy; Bees; Bees - drug effects; Bees - physiology; Bees - ultrastructure; behavior change; brain; Brain - drug effects; Brain - physiology; Brain - ultrastructure; brain of honey bee; Caspase; Caspase 1 - genetics; Caspase 1 - metabolism; Caspase-1; Caspase-3; caspases; Cell death; DNA; Dose-Response Relationship, Drug; fluorescent antibody technique; Honey; Imidacloprid; Imidazoles - toxicity; Immunofluorescence; In Situ Nick-End Labeling; Insect Proteins - genetics; Insect Proteins - metabolism; Insecticides; Insecticides - toxicity; messenger RNA; Microscopy, Electron, Transmission; Midgut; mRNA; Neonicotinoids; neurons; Neurons - drug effects; Neurons - physiology; Neurons - ultrastructure; Neurotoxicity; Nitro Compounds - toxicity; Occupational exposure; Pesticides; Phagocytosis; Pollinators; quantitative polymerase chain reaction; Real-Time Polymerase Chain Reaction; risk; RNA, Messenger - genetics; RNA, Messenger - metabolism; Salivary gland; Salivary glands; Transmission electron microscopy; worker honey bees
• ISSN: 0022-0493; 1938-291X
• DOI: 10.1093/jee/tov146

Honey bees are at an unavoidable risk of exposure to neonicotinoid pesticides, which are used worldwide. Compared with the well-studied roles of these pesticides in nontarget site (including midgut, ovary, or salivary glands), little has been reported in the target sites, the brain. In the current study, laboratory-reared adult worker honey bees (Apis mellifera L.) were treated with sublethal doses of imidacloprid. Neuronal apoptosis was detected using the TUNEL technique for DNA labeling. We observed significantly increased apoptotic markers in dose- and time-dependent manners in brains of bees exposed to imidacloprid. Neuronal activated caspase-3 and mRNA levels of caspase-1, as detected by immunofluorescence and real-time quantitative PCR, respectively, were significantly increased, suggesting that sublethal doses of imidacloprid may induce the caspase-dependent apoptotic pathway. Additionally, the overlap of apoptosis and autophagy in neurons was confirmed by transmission electron microscopy. It further suggests that a relationship exists between neurotoxicity and behavioral changes induced by sublethal doses of imidacloprid, and that there is a need to determine reasonable limits for imidacloprid application in the field to protect pollinators.