Enzymatic biomarkers as tools to assess environmental quality: A case study of exposure of the honeybee Apis mellifera to insecticides

Abstract

The present study was intended to evaluate the responses of enzymes in the honeybee Apis mellifera after exposure to deltamethrin, fipronil, and spinosad and their use as biomarkers. After determination of the median lethal doses (LD50), honeybees were exposed at doses of 5.07 ng/bee and 2.53 ng/bee for deltamethrin, 0.58 ng/bee and 0.29 ng/bee for fipronil, and 4.71 ng/bee and 2.36 ng/bee for spinosad (equivalent to 1/10th [LD50/10] and 1/20th [LD50/20] of the LD50, respectively). The responses of acetylcholinesterase (AChE), carboxylesterases (CaEs-1-3), glutathione-S-transferase (GST), catalase (CAT), and alkaline phosphatase (ALP) were assessed. The results showed that deltamethrin, fipronil, and spinosad modulated these biomarkers differentially. For the enzyme involved in the defense against oxidative stress, fipronil and spinosad induced CAT activity. For the remaining enzymes, 3 response profiles were identified. First, exposure to deltamethrin induced slight effects and modulated only CaE-1 and CaE-2, with opposite effects. Second, spinosad exhibited an induction profile for most of the biomarkers, except AChE. Third, fipronil did not modulate AChE, CaE-2, or GST, increased CAT and CaE-1, and decreased ALP. Thus, this set of honeybee biomarkers appears to be a promising tool to evaluate environmental and honeybee health, and it could generate fingerprints to characterize exposures to pesticides.

Biochemical response of the Africanized honeybee exposed to fipronil

“…In the present study, exposure to a sublethal dose of fipronil increased the enzyme activity of the 3 isoforms of CaE (CaE‐1, CaE‐2, and CaE‐3) in newly emerged and aged honeybees. Similar findings were reported by others using honeybees exposed to various pesticides (deltamethrin, fipronil, spinosad, and thiamethoxam) at sublethal doses. For this reason, and because these pesticides can modulate enzyme activity, CaEs have been used as biomarkers of exposure and as tools for assessing the first signs of toxicity to fipronil .…”

“…This response should be expected because AChE hydrolyzes acetylcholine, whereas the main mechanism of action of fipronil is by modulating the flow of chloride ions through inhibitory synapses . Similarly, Badiou‐Beneteau et al and Carvalho et al also observed no changes in the activity of AChE in response to exposure of A. mellifera mellifera to fipronil and thiamethoxam, suggesting that the lack of response is associated with the specificity of the mechanism of action and the exposure doses. In contrast, in a previous study, Badiou et al showed that AChE activity was significantly reduced when bees were exposed to deltamethrin and suggested that this response may be related to compensatory mechanisms and/or indirect effects of the metabolites of this pyrethroid.…”

“…In terms of these concerns, the main goal of the present study was to expose the Africanized honeybee to sublethal doses of a broad‐spectrum insecticide (fipronil) and to use biomarkers to assess the physiological condition of the bees. Therefore, we evaluated the hydrolases AChE and CaEs and the metabolic enzyme GST, both well recognized as important for insect lifespan and commonly used as biomarkers to assess the fitness of honeybees after exposure to an environmental stressor (e.g., fipronil) .…”

Combined neonicotinoid pesticide and parasite stress alter honeybee queens’ physiology and survival

“…To address physiological responses to stressor agents, infected or non-infected 8-days-old queens not yet mated, were analyzed just after pesticide exposure to a set of biochemical markers already tested on worker bees: CAT with a strong antioxidant action, GST involved in multiple metabolic functions including antioxidant activity and CaE α and CaE p implicated in detoxification2223. GST in head tissue is clearly induced by imidacloprid exposure and not by N. ceranae infection (Fig.…”

“…I: p – value = 0.0114687; N vs. NI: p – value = 0.5681849; I vs. NI: p – value = 0.3053523). CaE α is a phase-I enzyme that would therefore be directly involved in the detoxification of imidacloprid or might also responded to the production of other xenobiotics during intoxication and infection processes222325. Additionally, the expression of CaEs during development might also be regulated by other factors such as hormones28.…”