Abstract
Culex quinquefasciatus Say is a vector of many pathogens of humans, and both domestic and wild animals. Personal protection, reduction of larval habitats, and chemical control are the best ways to reduce mosquito bites and, therefore, the transmission of mosquito-borne pathogens. Currently, to reduce the risk of transmission, the pyrethroids, and other insecticide groups have been extensively used to control both larvae and adult mosquitoes. In this context, amino acids and acylcarnitines have never been associated with insecticide exposure and or insecticide resistance. It has been suggested that changes in acylcarnitines and amino acids profiles could be a powerful diagnostic tool for metabolic alterations. Monitoring these changes could help to better understand the mechanisms involved in insecticide resistance, complementing the strategies for managing this phenomenon in the integrated resistance management. The purpose of the study was to determine the amino acids and acylcarnitines profiles in larvae of Cx. quinquefasciatus after the exposure to different insecticides. Bioassays were performed on Cx. quinquefasciatus larvae exposed to the diagnostic doses (DD) of the insecticides chlorpyrifos (0.001 μg/mL), temephos (0.002 μg/mL) and permethrin (0.01 μg/mL). In each sample, we analyzed the profile of 12 amino acids and 31 acylcarnitines by LC-MS/MS. A t-test was used to determine statistically significant differences between groups and corrections of q-values. Results indicates three changes, the amino acids arginine (ARG), free carnitine (C0) and acetyl-carnitine (C2) that could be involved in energy production and insecticide detoxification. We confirmed that concentrations of amino acids and acylcarnitines in Cx. quinquefasciatus vary with respect to different insecticides. The information generated contributes to understand the possible mechanisms and metabolic changes occurring during insecticide exposure.
Highlights
The Culex pipiens complex comprises three main species: Culex pipiens Linnaeus, Culex quinquefasciatus Say and Culex pallens Coquillet [1]
We observed changes in the profile of three metabolites, two of which corresponded to acylcarnitines (C0 and C2) and one, to the amino acid arginine (ARG)
The metabolic levels from Cx. quinquefasciatus larvae exposed to three different insecticides were established
Summary
The Culex pipiens complex comprises three main species: Culex pipiens Linnaeus, Culex quinquefasciatus Say and Culex pallens Coquillet [1]. Pyrethroid resistance in Culex spp are conferred by two major mechanisms: detoxification by enhanced cytochrome P450 monooxygenases [25] as well as target site insensitivity (kdr) (i.e. an L1014F mutation in the voltage sodium channel gene) [26]. Culex populations may be affected by the extensive and intensive use of insecticides even when these species are not being targeted [31]). In this context, organophosphate (OP) and carbamate (CM) insecticides prevent the hydrolysis through inhibiting the enzyme acetylcholinesterase [32]. The cross-resistance is a problem involved in Culex where cytochrome monooxygenases (P450s) have particular interest as they are critical for the detoxification and/or activation of xenobiotics such as drugs, pesticides, plant toxins, chemical carcinogens and mutagens [33]
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