Mitochondrial dysfunction, oxidative stress, ER stress and mitochondria-ER crosstalk alterations in a chemical rat model of Huntington's disease: Potential benefits of bezafibrate.

Redox homeostasis, mitochondrial functions, and mitochondria-endoplasmic reticulum (ER) communication were evaluated in the striatum of rats after 3-nitropropionic acid (3-NP) administration, a recognized chemical model of Huntington's disease (HD). 3-NP impaired redox homeostasis by increasing malondialdehyde levels at 28 days, decreasing glutathione (GSH) concentrations at 21 and 28 days, and the activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and glutathione S-transferase at 7, 21, and 28 days, catalase at 21 days, and glutathione reductase at 21 and 28 days. Impairment of mitochondrial respiration at 7 and 28 days after 3-NP administration was also observed, as well as reduced activities of succinate dehydrogenase (SDH) and respiratory chain complexes. 3-NP also impaired mitochondrial dynamics and the interactions between ER and mitochondria and induced ER-stress by increasing the levels of mitofusin-1, and of DRP1, VDAC1, Grp75 and Grp78. Synaptophysin levels were augmented at 7 days but reduced at 28 days after 3-NP injection. Finally, bezafibrate prevented 3-NP-induced alterations of the activities of SOD, GPx, SDH and respiratory chain complexes, DCFH oxidation and on the levels of GSH, VDAC1 and synaptophysin. Mitochondrial dysfunction and synaptic disruption may contribute to the pathophysiology of HD and bezafibrate may be considered as an adjuvant therapy for this disorder.

Is there a risk to honeybees from use of thiamethoxam as a sugar beet seed treatment?

The ban imposed by the European Union on the use of neonicotinoids as sugar beet seed treatments was based on the exposure of bees to residues of neonicotinoids in pollen and nectar of succeeding crops. To address this concern, residues of thiamethoxam (TMX) and clothianidin (CTD) were analyzed in soil collected from fields planted in at least the previous year with thiamethoxam-treated sugar beet seed. This soil monitoring program was conducted at 94 sites across Germany in two separate years. In addition, a succeeding crop study assessed residues in soil, guttation fluid, pollen, and nectar sampled from untreated succeeding crops planted in the season after thiamethoxam seed-treated sugar beet at eight field sites across five countries. The overall mean residues observed in soil monitoring were 8.0 ± 0.5 µg TMX + CTD/kg in the season after the use of treated sugar beet seed. Residue values decreased with increasing time interval between the latest thiamethoxam or clothianidin application before sugar beet drilling and with lower application frequency. Residues were detected in guttation fluid (2.0-37.7 µg TMX/L); however, the risk to pollinators from this route of exposure is likely to be low, based on the reported levels of consumption. Residues of thiamethoxam and clothianidin in pollen and nectar sampled from the succeeding crops were detected at or below the limit of quantification (0.5-1 µg a.i./kg) in 86.7% of pollen and 98.6% of nectar samples and, unlike guttation fluid residues, were not correlated with measured soil residues. Residues in pollen and nectar are lower than reported sublethal adverse effect concentrations in studies with honeybee and bumble bee individuals and colonies fed only thiamethoxam-treated sucrose, and are lower than those reported to result in no effects in honeybees, bumble bees, and solitary bees foraging on seed-treated crops. Integr Environ Assess Manag 2022;18:709-721. © 2021 SYNGENTA. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Toxicological assessment of agrochemicals on bees using machine learning tools.

Machine learning (ML) is a branch of artificial intelligence (AI) that enables the analysis of complex multivariate data. ML has significant potential in risk assessments of non-target insects for modeling the multiple factors affecting insect health, including the adverse effects of agrochemicals. Here, the potential of ML for risk assessments of glyphosate (herbicide; formulation) and imidacloprid (insecticide, neonicotinoid; formulation) on the stingless bee Melipona quadrifasciata was explored. The collective behavior of forager bees was analyzed after in vitro exposure to agrochemicals. ML algorithms were applied to identify the agrochemicals that the bees have been exposed to based on multivariate behavioral features. Changes in the in situ detection of different proteins in the midgut were also studied. Imidacloprid exposure leads to the greatest changes in behavior. The ML algorithms achieved a higher accuracy (up to 91%) in identifying agrochemical contamination. The two agrochemicals altered the detection of cells positive for different proteins, which can be detrimental to midgut physiology. This study provides a holistic assessment of the sublethal effects of glyphosate and imidacloprid on a key pollinator. The procedures used here can be applied in future studies to monitor and predict multiple environmental factors affecting insect health in the field.

Dietary spirulina (Arthrospira platenesis) mitigated the adverse effects of imidacloprid insecticide on the growth performance, haemato-biochemical, antioxidant, and immune responses of Nile tilapia.

The present study was performed to evaluate the toxic effects of imidacloprid (IMI) insecticide on the growth performance, oxidative status, and immune response of Nile tilapia, Oreochromis niloticus (L.), and the protective role of dietary supplementation of spirulina, Arthrospira platensis, (SP). Fish (20.2 ± 0.5 g) were assigned to bifactorial design (2 IMI levels x 3 SP levels) to represent 6 treatments in triplicates. Spirulina was incorporated in diets at levels of 0.0 (control), 20, and 40 g/kg diet. Under each SP level, fish were exposed to 0.0 or 0.05 µg IMI/L. Fish in each treatment were fed on the corresponding diets up to apparent satiation thrice a day for 8 weeks. Two-way ANOVA revealed a significant decline in growth indices, hepatic superoxide dismutase, catalase, and glutathione peroxidase activities in the IMI-exposed fish. Contrariwise, serum alanine and aspartate aminotransferases, alkaline phosphatase, urea, creatinine, and malondialdehyde levels were markedly higher along with significant reductions of the reduced glutathione, nitric oxide as well as lysozyme values in the IMI-exposed fish group. The dietary supplementation of SP showed stimulating effects on the growth performance, haemato-biochemical, oxidants/antioxidants, and immune biomarkers of Nile tilapia with optimum level of 20 g SP/kg diet. Interestingly, the dietary supplementation of SP to Nile tilapia attenuated the above-mentioned variables with improving the growth performance, haemato-biochemical, oxidative stress, and immunity biomarkers. Therefore, the dietary supplementation of 20 g SP /kg diet could be a valuable candidate as a natural antioxidant for ameliorating the IMI toxicity in Nile tilapia.

A combination of Tropilaelaps mercedesae and imidacloprid negatively affects survival, pollen consumption and midgut bacterial composition of honey bee.

Tropilaelaps mercedesae is not only a major threat to honey bees in Asia but also a potential risk to global apiculture due to trade. Imidacloprid is a systemic insecticide that negatively affects individual bees. Moreover, the health of honey bees may be threatened by imidacloprid exposure and T. mercedesae infestation. We studied the effects of T. mercedesae and imidacloprid on the survival, food consumption and midgut bacterial diversity of Apis mellifera in the laboratory. Illumina 16S rRNA gene sequencing was used to determine the bacterial composition in the honey bee midgut. T. mercedesae decreased survival in parasitized honey bees compared with nonparasitized honey bees, but there was no significant difference in food consumption. The imidacloprid 50 µg/L diet significantly decreased syrup consumption of A. mellifera compared with the control diet. The combination of T. mercedesae infestation and imidacloprid 50 µg/L exposure reduced survival and increased pollen consumption of A. mellifera. T. mercedesae infestation or a combination of T. mercedesae infestation and exposure to 25 µg/L imidacloprid affected the midgut bacterial composition of honey bees. T. mercedesae infestation and imidacloprid exposure may reduce the survival and affect honey bee health.

Neonicotinoids in the agroecosystem: In-field long-term assessment on honeybee colony strength and microbiome.

Bees can be severely affected by various plant protection products (PPP). Among these, neonicotinoid insecticides are of concern as they have been shown to be responsible for extensive honeybee colonies death when released into the environment. Also, sublethal neonicotinoid doses contaminating single honeybees and their colonies (e.g. through contaminated pollen) are responsible for honeybees physiological alterations with probable implication also on microbiome functionality. Honeybees show symbiotic interactions with specific gut bacteria that can enhance the adult host performances. Among the known mechanisms, the modulation of the immune system, the degradation of recalcitrant secondary plant metabolites, pollen digestion, and hormonal signaling, are the most important functional benefits for the host honeybee. To date, few research efforts have aimed at revealing the impact of PPP on the gut microbial community of managed and wild honeybees. The majority of the existing literature relays on cage or semifield tests of short duration for research investigating neonicotinoids-gut microbiome interactions. This research wanted to unravel the impact of two neonicotinoids (i.e. imidacloprid and thiacloprid) in natural field conditions up to 5 weeks of exposure. A long-term impact of neonicotinoids on gut microbial community of honeybees was observed. The alterations affected several microbial genera and species such as Frischella spp., lactobacilli and bifidobacteria, whose shifting is implicated in intestinal dysbiosis. Long-term impact leading to dysbiosis was detected in case of exposure to imidacloprid, whereas thiacloprid exposure stimulated temporary dysbiosis. Moreover, the microbial diversity was significantly reduced in neonicotinoid-treated groups. Overall, the reported results support a compromised functionality of the gut microbial community, that might reflect a lower efficiency in the ecosystemic functionality of honeybees.

Mechanism study of the beneficial effect of sodium selenite on metabolic disorders in imidacloprid-treated garlic plants.

As an effective neonicotinoid insecticide, imidacloprid (IMI) has been widely used in crop production, but its residue affects normal plant growth. Selenium (Se) is a non-essential mineral nutrient in higher plants, that acts as the active centre of glutathione peroxidase (GSH-Px), which removes harmful peroxides. In this study, we investigated the mechanism by which selenium improves the growth status of IMI-treated garlic plants through analyses of apparent morphology and antioxidant enzyme activity as well as the dynamic changes in nutrients and metabolites in the plants. The results showed that 80 µg/kg Na2SeO3 had a strong effect on alleviating the damage in garlic plants exposed to IMI (1.2 mg/kg) by increasing the absorption of mineral elements to enhance the synthesis of chlorophyll and antioxidant enzymes. A nontarget metabolomics analysis based on gas chromatography-mass spectrometry (GC-MS) indicated that the addition of Na2SeO3 to IMI-treated garlic could reconstruct the plant metabolic distribution by enhancing the nitrogen and indole metabolism, maintaining lower concentrations of secondary metabolites and maintaining the balance of the plant energy metabolism. Our study provides novel insights into the molecular mechanisms by which garlic plants responds to IMI exposure and suggests the use of selenium with IMI-contaminated plants as a solution for the advancement of sustainable agricultural pesticide use.

Foliar persistence and residual activity of four insecticides of different mode of action on the predator Engytatus varians (Hemiptera: Miridae).

A greenhouse study was conducted to investigate the degradation kinetics of spinosad, flufenoxuron, dimethoate and imidacloprid in tomato (Solanum lycopersicum L.) foliage and their residual toxicity on Engytatus varians (Distant) (Hemiptera: Miridae), a predator of the tomato psyllid Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae). Insecticides were sprayed at 100% and 50% of their maximum field-registered concentrations (MFRC). Starting 6 h after spraying, leaf samples were taken every 10 d for 40 d and analyzed while E. varians adults were exposed to treated leaves to evaluate residual toxicity. Immediately after application at 100% MFRC, the residue concentrations were 73.34 µg g-1 spinosyn A and 59.2 µg g-1 spinosyn D, 9.21 µg g-1 flufenoxuron, 71.49 µg g-1 dimethoate and 31.74 µg g-1 imidacloprid. At 50% MFRC, initial residue concentrations were between 75% and 90% those at 100% MFRC. The estimated half-life (DT50) of spinosyns A and D, flufenoxuron, and dimethoate was between 34 and 40 d, while that of imidacloprid was 112 d. Flufenoxuron caused no mortality, while mortality due to spinosad was less than 10%, and only during the first 10 d. Mortality caused by either imidacloprid or dimethoate was around 100% up to 10 d after application, then decreased to around 30% after 40 d. Dimethoate toxicity was approximately proportional to residue concentration, while for imidacloprid there was an apparent threshold around 15 µg g-1. These results can be used to establish periods harmless for release of E. varians in the control of B. cockerelli on tomato crops under greenhouse conditions.

Dose-related impacts of imidacloprid oral intoxication on brain and liver of rock pigeon (Columba livia domestica), residues analysis in different organs.

Available data regarding Imidacloprid (IMI) insecticide hazards to birds are still being scare. Our study aimed to investigate toxic impacts of IMI oral gavage by different dose levels on the brain and liver of Rock pigeon (Columba livia domestica). Forty mature male birds were divided equally into four groups. A control group (C) was orally dosed Mazola corn oil and other three groups; the low dose (LD), the medium dose (MD), and the high dose (HD) groups were orally dosed IMI in Mazola corn oil by three dose levels corresponding to 1/15th, 1/10th, 1/5th IMI oral LD50 respectively. IMI exposure induced a significant decrease in serum levels of glutathione (GSH), superoxide dismutase (SOD) enzyme activity. On the other hand; malondialdehyde (MDA) levels were elevated. The levels of serum total protein, albumin, globulin, and A/G ratio showed a non-significant changes in all IMI dosed groups except levels of total protein in the HD IMI dosed group showed a significant decrease compared to the C group. Serum levels of alanine aminotransferase (ALT), lactate dehydrogenase (LDH), uric acid, plasma tumor necrosis factor α (TNFα) and plasma acetylcholinesterase (AChEs) enzyme activities showed a significant dose related increase in all IMI exposed groups compared to the C group; except the levels of ALT, LDH, and uric acid showed a non significant decrease in the LD IMI dosed group only. Residues of IMI were detected in the pectoral muscles, liver, brain, and kidney of all dosed rock pigeon. Moreover; pectoral muscles were the highest tissue for IMI residues detection. This is the first study reports accumulation of IMI in tissues other than crop, liver, and kidney of rock pigeon including brain and muscles. Moreover, the examined brain and liver tissues of all IMI dosed groups showed dosed related alterations in their structural and ultra-structural morphology. It is concluded that IMI oral administration to pigeon induced oxidative stress and detrimental effects in brain and liver of exposed pigeons. Additionally; IMI bio-accumulated in different organs being muscles is the highest tissues for IMI residues, thus monitoring of IMI residues in food is very essential.

Histone deacetylase inhibitor treatment restores memory-related gene expression and learning ability in neonicotinoid-treated Apis mellifera.

Apis mellifera plays crucial roles in maintaining the balance of global ecosystems and stability of agricultural systems by helping pollination of flowering plants, including many crops. In recent years, this balance has been disrupted greatly by some pesticides, which results in great losses of honeybees worldwide. Previous studies have found that pesticide-caused memory loss might be one of the major reasons for colony loss. Histone deacetylase inhibitors (HDACis) are chemical compounds that inhibit the activity of histone deacetylases and are known to cause hyperacetylation of histone cores and influence gene expression. In our study, the HDACi sodium butyrate was applied to honeybees as a dietary supplement. The effect of sodium butyrate on the expression profiles of memory-related genes was analysed by quantitative reverse transcription PCR. The results revealed that this HDACi had up-regulation effects on most of the memory-related genes in bees, even in bees treated with imidacloprid. In addition, using the proboscis extension reflex to evaluate olfactory learning in bees, we found that this HDACi boosted the memory formation of bees after impairment owing to imidacloprid exposure. This study investigated the association between gene expression and memory formation from an epigenetic perspective. Additionally, we further demonstrate the possibility of enhancing bee learning using HDACis and provide initial data for future research.

Lethal and Sublethal Effects on Tamarixia triozae (Hymenoptera: Eulophidae), an Ectoparasitoid of Bactericera cockerelli (Hemiptera: Triozidae), of Three Insecticides Used on Solanaceous Crops.

Lethal and sublethal effects of refined soybean oil, imidacloprid, and abamectin on Tamarixia triozae (Burks; Hymenoptera: Eulophidae) were assessed after exposure of the eggs, larvae, and pupae of this parasitoid to three concentrations of these active substances: the LC50 for fourth-instar Bactericera cockerelli (Sulc.; Hemiptera: Triozidae) and 50% and 100% of the minimum field-registered concentration (MiFRC). Soybean oil caused 26-61% mortality in T. triozae eggs and 6-19% in larvae; mortality in both eggs and larvae was ≤19% for imidacloprid and 4-100% for abamectin. All three compounds caused <18% mortality of T. triozae pupae, with the exception of the abamectin 50% (47%) and 100% (72%) MiFRC. The mortality of larvae and pupae derived from treated eggs was ≤39% for all three insecticides, and that of pupae derived from treated larvae was ≤10%. In general, emergence of adults developed from treated eggs, larvae, and pupae was affected more by abamectin than by the other treatments. The proportion of females derived from all three development stages was not affected by treatment with the compounds, except when the parasitoid was treated as larvae with the soybean oil 100 and 50% MiFRC (66 and 68%, respectively) or when treated as pupae with the imidacloprid LC50 and 100% MiFRC (~60%). Female longevity was generally higher than that of males. The use of imidacloprid, soybean oil, and abamectin in combination with T. triozae for pest control may be effective when the parasitoid is in the pupal stage because this stage is less susceptible than other immature stages.

Concentrations of imidacloprid and thiamethoxam in pollen, nectar and leaves from seed-dressed cotton crops and their potential risk to honeybees (Apis mellifera L.).

Neonicotinoid insecticides (NIs) have recently been recognized as co-factors in the decline of honeybee colonies because most neonicotinoids are systemic and can transfer into the pollen and nectar of many pollinated crops. In this study, we collected pollen, nectar and leaves from a cotton crop treated with imidacloprid and thiamethoxam to measure the residue levels of these two NIs at different application doses during the flowering period. Then, the residual data were used to assess the risk posed by the systemic insecticides to honeybees following mandated methods published by the European Food Safety Authority (EFSA), and a highly toxic risk to honeybees was highlighted. Imidacloprid was found in both pollen and nectar samples, whereas thiamethoxam was found in 90% of pollen samples and over 60% of nectar samples. Analysis of the pollen and nectar revealed residual amounts of imidacloprid ranging from 1.61 to 64.58 ng g-1 in the pollen and from not detected (ND) to 1.769 ng g-1 in the nectar. By comparison, the thiamethoxam concentrations in pollen and nectar ranged from ND to 14.521 ng g-1 and from ND to 4.285 ng g-1, respectively. The results of this study provide information on the transfer of two NIs from seed treatment to areas of the plant and provides an understanding of the potential exposure of the bee and other pollinators to systemic insecticides.

Antioxidant capacity of omega-3-fatty acids and vitamin E against imidacloprid-induced hepatotoxicity in Japanese quails.

Imidacloprid (IM) is a neonicotinoid insecticide, used in a wide range of agricultural activities worldwide. However, it results in ecosystem disturbances and signs of toxicity in human and animals. The current study was designed to elucidate the protective effects of omega-3-fatty acids (OFAs) and vitamin E (Vit E) against IM hepatotoxicity in Japanese quails. Seventy male quails (30 days old) were divided into seven groups (n = 10); G1 -ve control; G2 received IM (+ve control); G3 received OFA; G4 received Vit E; and G5, G6, and G7 received OFA and/or Vit E with IM for 30 days, respectively. Blood and liver tissue samples were collected. Imidacloprid significantly (p < 0.05) increased serum levels of alanine transferase (ALT), aspartate transferase (AST), triglycerides (TGC), and low-density lipoprotein cholesterol (LDL-C), as well as liver tissue malondialdehyde (MDA) concentration. Moreover, IM caused a significant (p < 0.05) decrease in the levels of serum high-density lipoprotein cholesterol (HDL-C), as well as liver superoxide dismutase (SOD) enzyme activity and reduced-glutathione (GSH) concentration in comparison to the -ve control group. Histopathological changes in hepatocytes, including thick cell trabeculae with marked hydropic vacuolar degeneration of cytoplasm, were found in IM-treated group. Treatment with OFA and/or Vit E resulted in significant improvements in general body condition, serum HDL-C level, and liver tissue SOD enzyme activity and GSH concentration, as well as significant decreases in the levels of serum AST, ALT, TGC, LDL-C, and hepatic tissue MDA. In conclusion, OFA and Vit E have a protective effect against IM toxicity, especially in their combination.

Comparison of the Toxic Effects of Quinolinic Acid and 3-Nitropropionic Acid in C. elegans: Involvement of the SKN-1 Pathway.

The tryptophan metabolite, quinolinic acid (QUIN), and the mitochondrial toxin 3-nitropropionic acid (3-NP) are two important tools for toxicological research commonly used in neurotoxic models of excitotoxicity, oxidative stress, energy depletion, and neuronal cell death in mammals. However, their toxic properties have yet to be explored in the nematode Caenorhabditis elegans (C. elegans) for the establishment of novel, simpler, complementary, alternative, and predictive neurotoxic model of mammalian neurotoxicity. In this work, the effects of QUIN (1-100 mM) and 3-NP (1-10 mM) were evaluated on various physiological parameters (survival, locomotion, and longevity) in a wild-type (WT) strand of C. elegans (N2). Their effects were also tested in the VC1772 strain (knock out for the antioxidant SKN-1 pathway) and the VP596 strain (worms with a reporter gene for glutathione S-transferase (GST) transcription) in order to establish the role of the SKN-1 pathway in the mode of action of QUIN and 3-NP. In N2, the higher doses of both toxins decreased survival, though only QUIN altered motor activity. Both toxins also reduced longevity in the VC1772 strain (as compared to N2 strain) and augmented GST transcription in the VP596 strain at the highest doses. The changes induced by both toxins require high doses, and therefore appear moderate when compared with other toxic agents. Nevertheless, the alterations produced by QUIN and 3-NP in C. elegans are relevant to mammalian neurotoxicity as they provide novel mechanistic approaches to the assessment of neurotoxic events comprising oxidative stress and excitotoxicity, in the nematode model.

Imidacloprid slows the development of preference for rewarding food sources in bumblebees (Bombus impatiens).

Bee pollination is economically and ecologically vital and recent declines in bee populations are therefore a concern. One possible cause of bee declines is pesticide use. Bumblebees exposed to imidacloprid, a neonicotinoid pesticide, have been shown to be less efficient foragers and collect less pollen on foraging trips than unexposed bees. We investigated whether bumblebees (Bombus impatiens) chronically exposed to imidacloprid at field-realistic levels of 2.6 and 10 ppb showed learning deficits that could affect foraging. Bumblebees were tested for their ability to associate flower colour with reward value in a simulated foraging environment. Bumblebees completed 10 foraging trips in which they collected sucrose solution from artificial flowers that varied in sucrose concentration. The reward quality of each artificial flower was predicted by corolla colour. Unexposed bumblebees acquired a preference for feeding on the most rewarding flower colour on the second foraging trip, while bumblebees exposed at 2.6 and 10 ppb did not until their third and fifth trip, respectively. The delay in preference acquisition in exposed bumblebees may be due to reduced flower sampling and shorter foraging trips. These results show that bumblebees exposed to imidacloprid are slow to learn the reward value of flowers and this may explain previously observed foraging inefficiencies associated with pesticide exposure.

Chemoprotective role of ethanol extract of Urtica urens L. against the toxicity of imidacloprid on endocrine disruption and ovarian morphometric in female rats, GC/MS analysis.

Imidacloprid (IMI) is a widely used in Tunisia and abroad, and high doses of IMI have been known to cause endocrine disruption. Some reports claim that Urtica urens L. (UU) can reduce toxicity thanks to it anti-inflammatory and antioxidant activities, but there is no scientific evidence justifying its use, which lets us think to its direct effect on the metabolism of the ovarian tissue. The present study was undertaken to evaluate the protective effect of UU against the toxicity of Confidor®, whose active substance is imidacloprid (IMI), in female rat, as well as the chemical compositions of UU ethanol (EtOH) extract by GC-MS. Female rats were divided into control group, 3 groups treated with IMI at 50, 200 or 300mg/kg/day and three groups co-treated with IMI (50, 200 or 300mg/kg/day)+100mg/kg/day of UU, for 60days. Blood samples were collected for the dosage of 17ß-estradiol levels. Ovaries were removed for tissular dosage of malondialdehyde (MDA), advanced oxidation protein products (AOPP), glutathione (GSH), vitamin E, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Histological and histomorphometric examinations were performed as well. IMI caused an acute ovary injury, increased the ovary tissue levels of MDA and AOPP, and decreased the levels of GSH, vitamin E, and antioxidant enzyme activities. The number and the diameter of follicles were markedly diminished together with a reduction of the relative weight of ovaries. Compared with controls, the treated rats exhibited a significant reduction in serum 17b-estradiol levels. These results suggest an endocrine disruption by IMI which may interfere with ovarian follicles development in rat. The injection of UU EtOH extract improved the histological and all biochemical parameters cited above. In conclusion, IMI induced an acute ovary injury accompanied with disturbance of oxidant status and causes follicular atresia. Significant antioxidant activities were also observed in UU EtOH and a total of 31 compounds were identified. The injection of UU EtOH provided a significant protection which might be due to its antioxidant activities.

Thiamethoxam and picoxystrobin reduce the survival and overload the hepato-nephrocitic system of the Africanized honeybee.

Apis mellifera perform important pollination roles in agroecosystems. However, there is often intensive use of systemic pesticides in crops, which can be carried to the colony by forage bees through the collection of contaminated pollen and nectar. Inside the colony, pollen loads are stored by bees that add honey and several enzymes to this pollen. Nevertheless, intra-colonial chronic exposure could induce sublethal effects in young bees exposed to a wide range of pesticides present in these pollen loads. This study was aimed to both determine the survival rate and evaluate the sublethal effects on the hepato-nephrocitic system in response to continuous oral exposure to lower concentrations of neonicotinoid thiamethoxam (TXT) and picoxystrobin fungicide (PXT). Exposure to a single chemical and co-exposure to both pesticides were performed in newly emerged honeybee workers. A significant decrease in the bee survival rates was observed following exposure to TXT (0.001 ng a.i./µL) and PXT (0.018 ng a.i./µL), as well as following co-exposure to TXT+PXT/2. After five days of continuous exposure, TXT induced sub-lethal effects in the organs involved in the detoxification of xenobiotics, such as the fat body and pericardial cells, and it also induced a significant increase in the hemocyte number. Thus, the hepato-nephrocitic system (HNS) reached the greatest level of activity of pericardial cells as an attempt to eliminate this toxic compound from hemolymph. The HNS was activated at low levels by PXT without an increase in the hemocyte number; however, the mobilization of neutral glycoconjugates from the trophocytes of the fat body was prominent only in this group. TXT and PXT co-exposure induced intermediary morphological effects in trophocytes and pericardial cells, but oenocytes from the fat body presented with atypical cytoplasm granulation only in this group. These data showed that the realistic concentrations of these pesticides are harmful to newly emerged Africanized honeybees, indicating that intra-colonial chronic exposure drastically reduces the longevity of bees exposed to neonicotinoid insecticide (TXT) and the fungicide strobilurin (PXT) as in single and co-exposure. Additionally, the sublethal effects observed in the organs constituting the HNS suggest that the activation of this system, even during exposure to low concentrations of theses pesticides, is an attempt to maintain homeostasis of the bees. These data together are alarming because these pesticides can affect the performance of the entire colony.

Chronic exposure to neonicotinoids reduces honey bee health near corn crops.

Experiments linking neonicotinoids and declining bee health have been criticized for not simulating realistic exposure. Here we quantified the duration and magnitude of neonicotinoid exposure in Canada's corn-growing regions and used these data to design realistic experiments to investigate the effect of such insecticides on honey bees. Colonies near corn were naturally exposed to neonicotinoids for up to 4 months-the majority of the honey bee's active season. Realistic experiments showed that neonicotinoids increased worker mortality and were associated with declines in social immunity and increased queenlessness over time. We also discovered that the acute toxicity of neonicotinoids to honey bees doubles in the presence of a commonly encountered fungicide. Our work demonstrates that field-realistic exposure to neonicotinoids can reduce honey bee health in corn-growing regions.

Application of the combination index (CI)-isobologram equation to research the toxicological interactions of clothianidin, thiamethoxam, and dinotefuran in honeybee, Apis mellifera.

Due to complex pest control scenarios and the needs of agricultural production, different neonicotinoids may be used in certain agricultural applications. Consequently, honeybees may be exposed to these substances through distribution throughout plant tissues via the vascular system through several pathways, such as surface water, the exudates excreted from plants, and air pollution via drift of dust as well as contaminated pollen and nectar. In the current study, the single and combined toxicity of clothianidin, dinotefuran, and thiamethoxam to honeybees was examined after 48 h exposure by the acute oral method and combination index (CI)-isobologram equation. At the 48 h interval, our results showed that 1) the order of toxicities for the single insecticides was ranked as clothianidin > thiamethoxam > dinotefuran and that 2) all binary and ternary combinations showed synergism or additive effect at the effect (fa) 0.5. Therefore, our results not only provided meaningful guidelines in evaluating the safety risk of the mixtures of the three neonicotinoids towards honeybees but also suggested that there is a significant interest in the study of mixture toxicities of neonicotinoids against honeybees because risk assessment of neonicotinoids against honeybees conducted only in individual insecticides may underestimate the realistic toxicity.

Overexpression of a cytochrome P450 and a UDP-glycosyltransferase is associated with imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata.

Current control of insect pests relies on chemical insecticides, however, insecticide resistance development by pests is a growing concern in pest management. The main mechanisms for insecticide resistance typically involve elevated activity of detoxifying enzymes and xenobiotic transporters that break-down and excrete insecticide molecules. In this study, we investigated the molecular mechanisms of imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), an insect pest notorious for its capacity to develop insecticide resistance rapidly. We compared the transcriptome profiles of imidacloprid-resistant and sensitive beetle strains and identified 102 differentially expressed transcripts encoding detoxifying enzymes and xenobiotic transporters. Of these, 74 were up-regulated and 28 were down-regulated in the resistant strain. We then used RNA interference to knock down the transcript levels of seven up-regulated genes in the resistant beetles. Ingestion of double-stranded RNA successfully knocked down the expression of the genes for three cytochrome P450s (CYP6BQ15, CYP4Q3 and CYP4Q7), one ATP binding cassette (ABC) transporter (ABC-G), one esterase (EST1), and two UDP-glycosyltransferases (UGT1 and UGT2). Further, we demonstrated that silencing of CYP4Q3 and UGT2 significantly increased susceptibility of resistant beetles to imidacloprid, indicating that overexpression of these two genes contributes to imidacloprid resistance in this resistant strain.