title: Fipronil and imidacloprid reduce honeybee mitochondrial activity.
abstract: Bees have a crucial role in pollination; therefore, it is important to determine the causes of their recent decline. Fipronil and imidacloprid are insecticides used worldwide to eliminate or control insect pests. Because they are broad-spectrum insecticides, they can also affect honeybees. Many researchers have studied the lethal and sublethal effects of these and other insecticides on honeybees, and some of these studies have demonstrated a correlation between the insecticides and colony collapse disorder in bees. The authors investigated the effects of fipronil and imidacloprid on the bioenergetic functioning of mitochondria isolated from the heads and thoraces of Africanized honeybees. Fipronil caused dose-dependent inhibition of adenosine 5'-diphosphate-stimulated (state 3) respiration in mitochondria energized by either pyruvate or succinate, albeit with different potentials, in thoracic mitochondria; inhibition was strongest when respiring with complex I substrate. Fipronil affected adenosine 5'-triphosphate (ATP) production in a dose-dependent manner in both tissues and substrates, though with different sensitivities. Imidacloprid also affected state-3 respiration in both the thorax and head, being more potent in head pyruvate-energized mitochondria; it also inhibited ATP production. Fipronil and imidacloprid had no effect on mitochondrial state-4 respiration. The authors concluded that fipronil and imidacloprid are inhibitors of mitochondrial bioenergetics, resulting in depleted ATP. This action can explain the toxicity of these compounds to honeybees.
authors.affiliation: Research Group of Ecology and Useful Insects, Animal Science, UNESP - Univ Estadual Paulista, Dracena, São Paulo, Brazil.
authors.forename: Daniel
authors.initials: D
authors.lastname: Nicodemo
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Maioli
authors.forename: Hyllana C D
authors.initials: HC
authors.lastname: Medeiros
authors.forename: Marieli
authors.initials: M
authors.lastname: Guelfi
authors.forename: Kamila V B
authors.initials: KV
authors.lastname: Balieira
authors.forename: David
authors.initials: D
authors.lastname: De Jong
authors.forename: Fábio E
authors.initials: FE
authors.lastname: Mingatto
mesh_terms: D000818:Animals; D001516:Bees / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007093:Imidazoles / Q000633:toxicity*; D007300:Insect Control; D007306:Insecticides / Q000633:toxicity*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000633:toxicity*; D011720:Pyrazoles / Q000633:toxicity*
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D011720:Pyrazoles; C082359:imidacloprid; C082360:fipronil
keywords: Honeybee; Insecticide; Mitochondria; Pesticide; Toxicity mechanism