Honey bees long-lasting locomotor deficits after exposure to the diamide chlorantraniliprole are accompanied by brain and muscular calcium channels alterations

Aklesso Kadala,Claude Collet,Pierre Charnet,Mercédès Charreton

doi:10.1038/s41598-019-39193-3

Abstract

Diamides belong to one of the newest insecticides class. We characterized cellular effects of the first commercialized diamide, chlorantraniliprole (ChlorAnt). ChlorAnt not only induces a dose-dependent calcium release from internal stores of honey bee muscle cells, but also a dose-dependent blockade of the voltage-gated calcium current involved in muscles and brain excitability. We measured a long lasting impairment in locomotion after exposure to a sublethal dose and despite an apparent remission, bees suffer a critical relapse seven days later. A dose that was sublethal when applied onto the thorax turned out to induce severe mortality when applied on other body parts. Our results may help in filling the gap in the toxicological evaluation of insecticides that has recently been pointed out by international instances due to the lack of suitable tests to measure sublethal toxicity. Intoxication symptoms in bees with ChlorAnt are consistent with a mode of action on intracellular calcium release channels (ryanodine receptors, RyR) and plasma membrane voltage-gated calcium channels (CaV). A better coupling of in vitro and behavioral tests may help in more efficiently anticipating the intoxication symptoms.

Highlights

Ryanodine receptors (RyR) are intracellular calcium release channels that are ubiquitously expressed in tissues of both vertebrates and invertebrates
To characterize the potency of chlorantraniliprole in inducing calcium release through honey bee muscle ryanodine receptors, muscle fibers isolated from the bee tibia were loaded with the intracellular calcium indicator Fluo-3 (Fig. 1A)
Muscle cells were perfused with increasing concentrations of chlorantraniliprole (1 nM, 10 nM, 100 nM, 30 seconds) and calcium was measured as a ΔF/F ratio (Fig. 1B)

Summary

Introduction

Ryanodine receptors (RyR) are intracellular calcium release channels that are ubiquitously expressed in tissues of both vertebrates and invertebrates. Chlorantraniliprole is the first commercialized member of the anthranilamic diamides class of insecticides. The rise of anthranilamides and other compounds targeting RyR was boosted by the 2004 patent application WO2004027042 that described the expression of a number of insect RyR full length genes in insect cell lines[14,15]. Most of these genes are those from the so called ‘insect pests’. Calcium release assays were made either on neurons from cockroach or on insect cells lines expressing RyR from the so called pests, but not on cells from beneficial insects (e.g. pollinators) such as bees. Quantitative locomotor approaches shed a new light on the deleterious sublethal effects of this molecule, the first commercialized anthranilic diamide insecticide

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