Development of biomarkers of exposure to xenobiotics in the honey bee Apis mellifera: Application to the systemic insecticide thiamethoxam

Abstract

This study describes the development of acetylcholinesterase (AChE), carboxylesterases (CaE1, CaE2, CaE3), glutathion-S-transferase (GST), alkaline phosphatase (ALP) and catalase (CAT) as enzyme biomarkers of exposure to xenobiotics such as thiamethoxam in the honey bee Apis mellifera. Extraction efficiency, stability under freezing and biological variability were studied. The extraction procedure achieved good recovery rates in one extraction step and ranged from 65 percent (AChE) to 97.3 percent (GST). Most of the enzymes were stable at -20°C, except ALP that displayed a slight but progressive decrease in its activity. Modifications of enzyme activities were considered after exposure to thiamethoxam at the lethal dose 50 percent (LD(50), 51.16 ng bee(-1)) and two sublethal doses, LD(50)/10 (5.12 ng bee(-1)) and LD(50)/20 (2.56 ng bee(-1)). The biomarker responses revealed that, even at the lowest dose used, exposure to thiamethoxam elicited sublethal effects and modified the activity of CaEs, GST, CAT and ALP. Different patterns of biomarker responses were observed: no response for AChE, an increase for GST and CAT, and differential effects for CaEs isoforms with a decrease in CaE1 and CaE3 and an increase in CaE2. ALP and CaE3 displayed contrasting variations but only at 2.56 ng bee(-1). We consider that this profile of biomarker variation could represent a useful fingerprint to characterise exposure to thiamethoxam in the honey bee A. mellifera. This battery of honey bee biomarkers might be a promising option to biomonitor the health of aerial and terrestrial ecosystems and to generate valuable information on the modes of action of pesticides.

Landscape and pesticide effects on honey bees: forager survival and expression of acetylcholinesterase and brain oxidative genes

“…On the one hand, the genes of the GST family are known to be upregulated in response to abiotic stresses, such as cold, heat, and insecticides (Yan et al 2013). On the other hand, AChE response to imidacloprid concentrations are similar to what has been found by Badiou-Bénéteau et al (2012), in which bees fed in the lab with thiamethoxam lethal doses showed no AChE response, although the same authors suggested that AChE expression could be considered a robust biomarker for other insecticide exposure in living bees (Badiou et al 2008). Previous field and laboratory studies investigating the neonicotinoid impact on honey bee survival (more precisely on the AChE activity) reported elevated levels of AChE activity in honey bee brains when subjected to thiamethoxam or clothianidin (Boily et al 2013;Alburaki et al 2015).…”

Low dietary levels of Al, Pb and Cd may affect the non-enzymatic antioxidant capacity in caged honey bees (Apis mellifera)

“…Therefore, concentrations of Pb combined with the 10-day exposure in our study might not have been sufficient to influence the honey bee's MTLPs. Another study conducted at La Reunion Island by Badiou-B en eteau et al (2012) reported higher MT levels in honey bees from an urban area compared to a semi-natural environment. This time, the levels of MT were 10e100 times higher than the values we measured in our study.…”

“…However, several exposures and methodological parameters make direct comparison difficult. Our protocol was limited to 10 days in the laboratory using one metal at a time whereas the study of Badiou-B en eteau et al (2012) lasted one year in natural environments in the presence of several organic and inorganic contaminants, and metal accumulation in bees was not measured. Moreover, several methodological differences must be considered notably instruments for detection and tissues selected for analysis.…”

“…Increased expression of MTs, a widespread and well-conserved protective mechanism against metal toxicity, has been characterized in Drosophila (Zhang et al, 2001). MTs have not yet been annotated in Apis mellifera, and to our knowledge, there is only one study on metal induction of MTLPs in this species (Badiou-B en eteau et al, 2012).…”

In vitro effects of thiamethoxam on larvae of Africanized honey bee Apis mellifera (Hymenoptera: Apidae)

“…It has been established that thiamethoxam, a member of the nitro-containing neonicotinoid group, is toxic to A. mellifera (Iwasa et al, 2004;Badiou-Bénéteau et al, 2012). Because this insecticide is systemic, it should be considered hazardous to pollinators once the nectar, pollen and exudates can be contaminated (Girolami et al, 2009;Goulson, 2013;Godfray et al, 2014).…”