Behavioral and metabolic effects of sublethal doses of two insecticides, chlorpyrifos and methomyl, in the Egyptian cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae)

International audienceInsecticides have long been used as the main method in limiting agricultural pests, but their widespread use has resulted in environmental pollution, development of resistances, and biodiversity reduction. The effects of insecticides at low residual doses on both the targeted crop pest species and beneficial insects have become a major concern. In particular, these low doses can induce unexpected positive (hormetic) effects on pest insects, such as surges in population growth exceeding what would have been observed without pesticide application. Methomyl and chlorpyrifos are two insecticides commonly used to control the population levels of the cotton leafworm Spodoptera littoralis, a major pest moth. The aim of the present study was to examine the effects of sublethal doses of these two pesticides, known to present a residual activity and persistence in the environment, on the moth physiology. Using a metabolomic approach, we showed that sublethal doses of methomyl and chlorpyrifos have a systemic effect on the treated insects. We also demonstrated a behavioral disruption of S. littoralis larvae exposed to sublethal doses of methomyl, whereas no effects were observed for the same doses of chlorpyrifos. Interestingly, we highlighted that sublethal doses of both pesticides did not induce a change in acetylcholinesterase activity in head of exposed larva

Gut Pathology and Responses to the Microsporidium Nosema ceranae in the Honey Bee Apis mellifera

The microsporidium Nosema ceranae is a newly prevalent parasite of the European honey bee (Apis mellifera). Although this parasite is presently spreading across the world into its novel host, the mechanisms by it which affects the bees and how bees respond are not well understood. We therefore performed an extensive characterization of the parasite effects at the molecular level by using genetic and biochemical tools. The transcriptome modifications at the midgut level were characterized seven days post-infection with tiling microarrays. Then we tested the bee midgut response to infection by measuring activity of antioxidant and detoxification enzymes (superoxide dismutases, glutathione peroxidases, glutathione reductase, and glutathione-S-transferase). At the gene-expression level, the bee midgut responded to N. ceranae infection by an increase in oxidative stress concurrent with the generation of antioxidant enzymes, defense and protective response specifically observed in the gut of mammals and insects. However, at the enzymatic level, the protective response was not confirmed, with only glutathione-S-transferase exhibiting a higher activity in infected bees. The oxidative stress was associated with a higher transcription of sugar transporter in the gut. Finally, a dramatic effect of the microsporidia infection was the inhibition of genes involved in the homeostasis and renewal of intestinal tissues (Wnt signaling pathway), a phenomenon that was confirmed at the histological level. This tissue degeneration and prevention of gut epithelium renewal may explain early bee death. In conclusion, our integrated approach not only gives new insights into the pathological effects of N. ceranae and the bee gut response, but also demonstrate that the honey bee gut is an interesting model system for studying host defense responses

Exposure to Sublethal Doses of Fipronil and Thiacloprid Highly Increases Mortality of Honeybees Previously Infected by Nosema ceranae

International audienceBACKGROUND: The honeybee, Apis mellifera, is undergoing a worldwide decline whose origin is still in debate. Studies performed for twenty years suggest that this decline may involve both infectious diseases and exposure to pesticides. Joint action of pathogens and chemicals are known to threaten several organisms but the combined effects of these stressors were poorly investigated in honeybees. Our study was designed to explore the effect of Nosema ceranae infection on honeybee sensitivity to sublethal doses of the insecticides fipronil and thiacloprid. METHODOLOGY/FINDING: Five days after their emergence, honeybees were divided in 6 experimental groups: (i) uninfected controls, (ii) infected with N. ceranae, (iii) uninfected and exposed to fipronil, (iv) uninfected and exposed to thiacloprid, (v) infected with N. ceranae and exposed 10 days post-infection (p.i.) to fipronil, and (vi) infected with N. ceranae and exposed 10 days p.i. to thiacloprid. Honeybee mortality and insecticide consumption were analyzed daily and the intestinal spore content was evaluated 20 days after infection. A significant increase in honeybee mortality was observed when N. ceranae-infected honeybees were exposed to sublethal doses of insecticides. Surprisingly, exposures to fipronil and thiacloprid had opposite effects on microsporidian spore production. Analysis of the honeybee detoxification system 10 days p.i. showed that N. ceranae infection induced an increase in glutathione-S-transferase activity in midgut and fat body but not in 7-ethoxycoumarin-O-deethylase activity. CONCLUSIONS/SIGNIFICANCE: After exposure to sublethal doses of fipronil or thiacloprid a higher mortality was observed in N. ceranae-infected honeybees than in uninfected ones. The synergistic effect of N. ceranae and insecticide on honeybee mortality, however, did not appear strongly linked to a decrease of the insect detoxification system. These data support the hypothesis that the combination of the increasing prevalence of N. ceranae with high pesticide content in beehives may contribute to colony depopulation

Modes d'action des néonicotinoïdes (étude comparée des mécanismes d'absorption et de métabolisation chez un invertébré, l'abeille domestique (Apis mellifera L.), et chez un vertébré, l'homme)

Le rôle de l'absorption et de la métabolisation dans la toxicité différentielle de l'acétamipride (AAP) et de l'imidaclopride (IMI) est évalué chez l'abeille et chez l'Homme. Chez l'abeille, l'absorption et la distribution de l'AAP sont très rapides et similaires à celles de l'IMI. Les métabolites de l'AAP tendent à persister dans l'organisme et diffèrent de ceux de l'IMI, expliquant la toxicité différente des deux molécules. L'absorption des deux molécules, étudiée au moyen de la lignée cellulaire humaine Caco-2, permet de prédire une absorption intestinale importante. Les mécanismes de transports passifs et actifs impliqués diffèrent pour les deux molécules. Chez l'homme, la métabolisation de l'AAP par des hépatocytes et par des microsomes hépatiques conduit à un seul métabolite en impliquant majoritairement le cytochrome P450 CYP2C9 dont l'hétérogénéité au sein de la population induirait un risque sanitaire différent pour les individus si le seul métabolite de l'AAP était toxiqueAIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Action des insecticides organophosphates et carbamates sur l'abeille Apis Mellifera. Aspects toxicologiques et pharmacologiques

AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Caractérisation cinétique et moléculaire du biomarqueur acétylcholinestérase chez l'abeille, Apis mellifera

L'acétylcholinesterase (AChE, EC 3.1.1.7) est un marqueur biologique de contamination environnementale très étudiée et très utilisée dans les milieux aquatiques. La nécessité de développer des outils de surveillance de la qualité des milieux terrestres et aériens nous a conduit à approfondir les connaissances de l'AChE de l'abeille, Apis mellifera. L'identification et la purification des différentes formes d'AChE présentes ont révélé l'existence de deux formes membranaires, AChEm1 et AChEm2, et d'une forme soluble majoritaire, AChEsol1. Les deux formes membranaires représentent 95% de l'activité totale et leurs propriétés physcico-chimiques ont été déterminées. La caractérisation cinétique, à l'état stationnaire et pré-stationnaire, de l'ensemble des formes a fourni des renseignements sur leurs propriétés catalytiques ainsi que sur leur dynamique conformationnelle. Un équilibre lent entre plusieurs états conformationnels pré-existants a été mis en évidence pour chacune des formes d'AChE ainsi que pour la forme soluble de Drosophila melanogaster. Cet équilibre pourrait être à la base d'un mécanisme de protection aux toxiques. Enfin, une étude comparée (in vivo/in vitro) de l'effet de la deltaméthrine (pyréthrinoïde) sur les différentes formes de l'AChE est présentée et permet de proposer une nouvelle perspective d'utilisationde l'AChE en tant que biomarqueur.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

ETUDE PHARMACOCINETIQUE ET PHARMACODYNAMIQUE DE LA LETALITE INDUITE PAR L'IMIDACLOPRIDE ET SES METABOLITES CHEZ L'ABEILLE DOMESTIQUE (APIS MELLIFERA L.)

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Suivi de la trajectoire tridimensionnelle de vers de terre marqués dans des colonnes de sol artificielles

National audienc

Trajectoires en trois dimensions de vers de terre marqués au cobalt-60 dans des colonnes de sol artificielles

International audienc

Intestinal absorption of the acetamiprid neonicotinoid by Caco-2 cells: transepithelial transport, cellular uptake and efflux.

International audienceThe human intestinal absorption of acetamiprid (AAP) using the Caco-2 cell line reveals that AAP flux was active in a bidirectional mode with an apparent permeability coefficient of 26 x 10(-6) cm x s(-1) at 37 degrees C. Apical uptake was concentration-dependent and unsaturated for AAP concentrations up to 200 micro M. AAP cell preloading demonstrated the involvement of active transport mechanisms. Arrhenius plot analysis revealed an unusual profile with two apparent activation energies suggesting two transport processes. Uptake Vi studies indicated the involvement of a sodium-dependent transporter, the presence of a common transporter of AAP and nicotine and the involvement of Ti-sensitive ATP-dependent efflux transporters. Apical efflux investigations showed the involvement of inward active transporter(s). Whereas vincristine had no effect on intracellular accumulation, taxol and daunorubicin treatments unexpectedly led to 10% and 23% reductions respectively, suggesting that the latter shared a common inward transporter with AAP. All these results suggest full and express AAP absorption in vivo with transport involving both inward and outward, passive and active mechanisms. Thus, AAP or its metabolites could be representative of a risk for human health after its ingestion in food