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Environmental Toxicology and Pharmacology
Volume 20, Issue 1,
July 2005
, Pages 18-21
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Abstract
We investigated interactions of the neonicotinoid insecticide imidacloprid with the nicotinic acetylcholine-regulated receptors (nAcChR) of embryonic frog muscle cells. The response of the muscle cells to acetylcholine, nicotine and imidacloprid was monitored as cell contractions. Acetylcholine was more potent than nicotine (EC50=5×10−8M versus 6×10−7M) in this physiological test system. Contractions induced by acetylcholine or nicotine were both blocked by α-bungarotoxin (IC50=9×10−7M). Imidacloprid itself did not cause cell contractions but at concentrations ≥3.3×10−6M prevented or attenuated those induced by acetylcholine (5×10−7M and 5×10−5M) or nicotine (5×10−6M to 5×10−3M). The dose response relationship between acetylcholine or nicotine, imidacloprid and cell contractions suggests that imidacloprid is an antagonist at the nAcChR of the muscle cells in contrast to its established role as an agonist in its toxic action on insect neural receptors. In chicken embryos, imidacloprid caused arthrogryposis, presumably due to its interference with the embryonic neuromuscular nAcChR. A magnitude of imidacloprid dose that caused arthrogryposis indicates a negligible teratogenic potential of imidacloprid when applied for the insect pest control.
Introduction
Neonicotinoids are a group of recently developed insecticides that act as agonists on insect neural nicotinic acetylcholine-regulated receptors (nAcChR) (Yamamoto and Casida, 1999). In contrast to nicotine, they are toxic selectively to insects mainly because of the structural differences between the insect and vertebrate nAcChR that result in their higher affinity for the insect neural receptors (Tomizawa et al., 2003). Response of the nAcChR to neonicotinoids is determined by the composition of receptor subunits and molecular features of the neonicotinoid. While their action on the neural nAcChR is well documented (Ihara et al., 2003, Nagata et al., 1998, Tomizawa and Casida, 2003), less is known about their interactions with the neuromuscular nAcChR.
In this paper, we report our investigation of interactions of a neonicotinoid imidacloprid with the nAcChR of embryonic frog muscle cells in order to assess imidacloprid potential to alter embryonic muscle-skeletal development. Imidacloprid was chosen as a primary model neonicotinoid because of its long history of use and best understood mechanism of action (Yamamoto and Casida, 1999). Embryonic frog muscle cells were used as a representative of a nonneural nAcChR target, composed of subunits in a manner distinct from the one that forms the neural receptors (Tomizawa and Casida, 2003). They are easy to prepare (Stollberg and Fraser, 1988) and monitoring their response to acetylcholine and its agonists/antagonists as cell contraction better reflects their in vivo functioning than any other method. We also examined imidacloprid potential to alter embryonic development of chicken embryos, presumably via its interference with the neuromuscular (pre)nAcChR that have molecular features similar to those of embryonic frog muscle cells (Lindstrom et al., 1990). We focused on malformations such as arthrogryposis since it is the major tibiofemural defect in organophosphate-induced teratogenesis in chicken embryos caused by acetylcholine accumulated due to acetylcholinesterase inhibition by organophosphates (summarized by Seifert and Casida, 1981, Seifert and Casida, 1981). Nicotine was used as a well-established nAcChR agonist and as a positive control of nicotine-induced teratogenicity in chicken embryos (Gatling and Jackson, 1964), respectively.
Section snippets
Chemicals
Imidacloprid {1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine} (99% purity) was purchased from Chem Service (West Chester, PA, USA). Acetylcholine chloride was from Nutritional Biochemicals Corporation (Cleveland, OH, USA). (-)Nicotine (98–100% purity), α-bungarotoxin (Bungarus multicinctus) and other chemicals of the highest available purity were obtained from Sigma (St. Louis, MO, USA).
Embryonic frog muscle cell culture (Stollberg and Fraser, 1988)
Eggs of Xenopus laevis were fertilized and incubated at 22°C for about 24h. Somites from the
Results
The frog embryonic muscle cells were responsive to both acetylcholine and nicotine. Acetylcholine induced contractions of the muscle cells at concentrations about ten times lower than nicotine (EC50=5×10−8M versus 6×10−7M) (Fig. 2, Fig. 3). Both acetylcholine- and nicotine-induced muscle contractions were blocked by α-bungarotoxin (IC50=9×10−7M).
Imidacloprid did not induce cell contractions in a wide concentration range from 3.3×10−11M to 5×10−4M. It did, however, prevent or attenuate both the
Discussion
The distinct response of embryonic frog muscle cells to imidacloprid, and acetylcholine or nicotine respectively, revealed two principle differences between their actions at the nAcChR of the neuromuscular junction. First, unlike in its action on insect neural nAcChR, and in contrast to acetylcholine and nicotine (Fig. 2, Fig. 3), imidacloprid is not an agonist at the embryonic frog muscle cell nAcChR. Second, imidacloprid alters the response of the muscle cells to both acetylcholine and
Acknowledgements
This work is contributed as Journal Series No. 4691 of the College of Tropical Agriculture and Human Resources.
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Science production of pesticide residues in honey research: A descriptive bibliometric study
2020, Environmental Toxicology and Pharmacology
Citation Excerpt :
Neonicotinoids are a group of insecticides that include nitenpyram, dinotefuran, thiamethoxam, imidacloprid, clothianidin, acetamiprid, and thiacloprid (Xiao et al., 2011). Neonicotinoids act as agonists on insect neural nicotinic acetylcholine-regulated receptors (nAcChR) (Seifert and Stollberg, 2005), causing over-stimulation to nerve cells and resulting in paralysis and death (Wang et al., 2020). This group of pesticides is less toxic to mammals due to the highly selective affinity to nAcChRs of insects over vertebrate (Xiao et al., 2011).
This work aims to provide a comprehensive study of the available research information on pesticide residues in honey through literature analysis. The research advancements within this research field from 1948 to 2019 are addressed using the Web of Science database. The results from the 685 articles analyzed indicate that this research field is in the focus of interest nowadays (Price index: 47.5%). The yearly production increased steadily from 2001 on, and authors, journals, and institutions followed Lotka’s law. On the other hand, Pico, Y (Spain) (2.5%), Journal of Chromatography A (5.8%), the USA (15.0%) and Agricultural Research Service (USA) (4.0%) were the most productive author, journal, country and institution, respectively. The research hotspots of this field, according to keyword analysis, are related to the chromatographic techniques for the determination of pesticides such as imidacloprid, neonicotinoids, or coumaphos in honey and derivate products such as propolis and wax.
The effects of neonicotinoid exposure on embryonic development and organ mass in northern bobwhite quail (Colinus virginianus)
2017, Comparative Biochemistry and Physiology Part - C: Toxicology and Pharmacology
Citation Excerpt :
Dichlorodiphenyltrichloroethane (DDT) has been known to cause skeletal and beak abnormalities in birds (Fry, 1995) while imidacloprid and clothianidin have produced testicular deformities as well as malformed ribs, vertebrae, and phalanges in vertebrate species, with doses based on recommended rates of application (Gawade et al., 2013, Gibbons et al., 2014). Additionally, imidacloprid's interference with neuromuscular nAChRs has been identified as a mechanism for causing curvature of the joints in embryos (Seifert and Stollberg, 2005). The causal pathway of the observed deformities and mass differences is not immediately clear from the results, but previous work suggests that altered gene transcription rates may be a potential factor.
Since their emergence in the early 1990s, neonicotinoid use has increased exponentially to make them the world's most prevalent insecticides. Although there has been considerable research concerning the lethality of neonicotinoids, their sub-lethal and developmental effects are still being explored, especially with regard to non-mammalian species. The goal of this research was to investigate the effects of the neonicotinoid imidacloprid on the morphological and physiological development of northern bobwhite quail (Colinus virginianus). Bobwhite eggs (n=390) were injected with imidacloprid concentrations of 0 (sham), 10, 50, 100, and 150mg/kg of egg mass, which was administered at day 0 (pre-incubation), 3, 6, 9, or 12 of growth. Embryos were dissected, weighed, staged, and examined for any overt structural deformities after 19days of incubation. The mass of the embryonic heart, liver, lungs and kidneys was also recorded. The majority of treatments produced no discernible differences in embryo morphology; however, in some instances, embryos were subject to increased frequency of anatomical deformity and altered organ masses. Some impacts were more pronounced in specific dosing periods, implying that there may be critical windows of development when embryos are more susceptible to neonicotinoid exposure. This investigation suggests that imidacloprid has the potential to impact bobwhite quail embryonic development and chick survival.
Study on embryonic effects of neonicotinoid insecticide on chick embryos
2014, Journal of the Anatomical Society of India
Citation Excerpt :
Increased use of chemical pesticides has resulted in contamination of the environment and many associated long-term effects on human health, ranging from short-term impacts such as headaches and nausea to chronic impacts such as cancer, reproductive harm, and endocrine disruption.3 Imidacloprid interacts with the acetylcholine receptor, which is widely conserved across species.4 In the past few years the agricultural production has been enormously enhanced by the use of many synthetic pesticides.
Neonicotinoids are a group of insecticides derived from nicotine isolated from the tobacco plant. Imidacloprid is a widely applied pesticide due to their higher affinity for insect nicotinic acetylcholine receptors. Like nicotine, it acts on nervous system. Worldwide, it is considered to be one of the insecticides used in the largest volume. It has a wide diversity of uses in agriculture, on turf, on pets, and for household pests.
Present study was carried out in the Department of Anatomy Government Medical College, Ambedkar Nagar and Santosh Medical College Ghaziabad U.P. on 280 fertile eggs of white leghorn chicken obtained from government poultry farm after taking permission from animal ethical committee. Chicken eggs after having been exposed to Imidacloprid with doses of 5μg, 12.5μg, 25μg, and 50μg in a volume of 5μl, 12.5μl, 25μl and 50μl respectively and control same as test group. The embryos were terminated on 18th and 20th days, egg shell broken with a scalpel and embryos removed. Gross abnormalities observed and recorded in all embryos.
The results show that experimental group had comparatively more cases of delayed and growth retardation resulting into failure of retraction of yolk sac, limbs defects, neural tube defects as compared to controls. Comparatively higher doses proved more toxic and also caused many developmental defects.
Neonicotinoid exposure increases the risks of developmental defects with increasing embryonic age. Imidacloprid caused developmental delays and defects on nervous system.
Development of biomarkers of exposure to xenobiotics in the honey bee Apis mellifera: Application to the systemic insecticide thiamethoxam
2012, Ecotoxicology and Environmental Safety
Citation Excerpt :
Neonicotinoids can induce toxicity via distinct pathways. They can act agonistically on the nicotinic acetylcholine receptor (Tomizawa and Yamamoto, 1993) but may also exhibit an antagonist action on nicotinic acetylcholine receptors (nAChR) (Seifert and Stollberg, 2005). However, it has been suggested that the toxicity of neonicotinoids may be connected to the existence of high and low affinity binding sites, which implies a more complex mode of action (Nagata et al., 1998; Suchail et al., 2001; Guez et al., 2001, 2003).
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 (LD50, 51.16ngbee−1) and two sublethal doses, LD50/10 (5.12ngbee−1) and LD50/20 (2.56ngbee−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 2.56ngbee−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.
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Extensive use of neonicotinoid insecticides has raised great concerns about their ecological risk. A reliable method to measure trace neonicotinoids in complicated aquatic environment is a premise for assessing their aquatic risk. To effectively remove matrix interfering substances from field water samples before instrumental analysis with HPLC/MS/MS, a multi-sorbent solid phase extraction method was developed using Box-Behnken design. The optimized method employed 200mg HLB/GCB (w/w, 8/2) as the sorbents and 6mL of 20% acetone in acetonitrile as the elution solution. The method was applied for measuring neonicotinoids in water at a wide range of concentrations (0.03–100μg/L) containing various amounts of matrix components. The recoveries of acetamiprid, imidacloprid, thiacloprid and thiamethoxam from the spiked samples ranged from 76.3% to 107% while clothianidin and dinotefuran had relatively lower recoveries. The recoveries of neonicotinoids in water with various amounts of matrix interfering substances were comparable and the matrix removal rates were approximately 50%. The method was sensitive with method detection limits in the range of 1.8–6.8ng/L for all target neonicotinoids. Finally, the developed method was validated by measurement of trace neonicotinoids in natural water.
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