Effects of pyriproxyfen on zebrafish brain mitochondria and acetylcholinesterase

Pyriproxyfen toxicity to fish and crustaceans: A literature review

Pyriproxyfen (PPF) is an insect growth regulator (IGR) that acts as a juvenile hormone agonist (JHA). It is widely used as a larvicide to control insect vectors, as antiparasitic medicines, and for pest control in domestic and agricultural environments. Reports in the literature show that PPF is toxic to fish and non-target crustaceans. Therefore, this review aimed to compile and analyze the state of the art on PPF toxicity to fish and crustaceans. We conducted a comprehensive and critical review by searching combinations of English keywords on the main scientific databases. The articles were selected based on inclusion and exclusion criteria. The findings demonstrated that exposure to different concentrations of PPF can have toxic effects on fish and crustaceans, resulting in histopathological damage to vital organs, reproductive dysfunction, and genetic changes. In crustaceans, PPF caused changes in fecundity, increased male production, and induced changes in offspring. In fish, histopathological changes were identified in organs such as the heart, liver, kidneys, brain, and gonads. Regarding reproduction, an increase in spermatogonial cysts in the testicles was reported, as well as the occurrence of atresia of oocytes in the female gonads. Furthermore, changes in the activity of antioxidant enzymes, the presence of reactive oxygen species indicating oxidative stress and alterations in the expression of genes related to thyroid and growth hormones were induced by exposure of fish to PPF.

Development and evaluation of S-carboxymethyl-L-cystine-loaded solid lipid nanoparticles for Parkinson's disease in murine and zebrafish models

Parkinson's disease (PD) is an advanced neurodegenerative condition distinguished by the rapid decline of dopamine neurons in the midbrain, leading to an imbalance in dopamine and acetylcholine levels, precipitating associated symptoms. The main objective of this work was to fabricate solid lipid nanoparticles (SLNs) loaded with S-carboxymethyl-L-cystine (SC) for enhanced delivery to the brain. This study examines the impact of these SLNs on rotenone (RT) caused Parkinson's disease (PD) in both rat and zebrafish models. The process of loading SC into SLNs was achieved through the solvent evaporation-emulsification method. The SC-encapsulated solid lipid nanoparticles (SCSLNs) were subjected to physicochemical evaluation, and their properties were verified. For 28 days, the rats received subcutaneous injections of RT at a dosage of 2 mg × kg-1 body weight. Additionally, the rats in the experimental group received SCSLNs from the 14th to the 28th days of the trial. Interestingly, the locomotor activity, grip strength, and exploratory behaviour of the rats with SCSLNs significantly improved. Furthermore, it was observed that the quantities of acetylcholinesterase (AchE) inside the brain tissue had increased, and oxidative biomarkers had decreased. In addition, there was a discernible decrease in Lewy body development and cellular damage compared to the positive control group. Zebrafish were dosed with SCSLNs simultaneously as they were subjected to a 5 µg × L-1 RT concentration for 28 days during the experiment. AchE levels in the fish brain increased, resulting in improved locomotor activity in the SCSLN group of zebrafish. The findings of this investigation imply that using SCSLNs may reduce Parkinson's disease symptoms via enhanced delivery of SC into the brain.

Pyriproxyfen, villain or good guy? A brief review

Pyriproxyfen (PPF) acts as a juvenile growth regulator, interfering with normal metamorphosis and blocking the development of insects into adulthood. Although the World Health Organization (WHO) considers the use of PPF at a concentration of 0.01 mg/L as unlikely to pose health risks, recent studies have unveiled potential risks associated with PPF exposure to non-target organisms. Exposure to PPF disrupts insect development primarily by mimicking juvenile hormones; therefore, concerns linger over its impact on unintended species. Studies have highlighted the adverse effects of PPF on aquatic invertebrates, fish, and amphibians and revealed mortality and developmental abnormalities in non-target mosquito species exposed to PPF-treated water. Moreover, PPF may act as an endocrine disruptor, interfering with hormonal pathways crucial for growth, reproduction, and behavior in exposed organisms. Amphibians, for instance, display altered reproductive physiology and developmental abnormalities due to disruptions in endocrine signaling pathways caused by PPF. The ecological ramifications of PPF extend beyond direct toxicity to non-target species. Indirect effects include shifts in food web dynamics and ecosystem functioning. Reductions in insect populations, induced by PPF, can disrupt food availability for higher trophic levels, potentially destabilizing community structure and ecosystem equilibrium. Given mounting evidence of unintended consequences, robust risk assessment and regulatory oversight are imperative. Accurate classification of PPF by regulatory bodies is essential to balancing its role in disease control and pest management benefits with the need to safeguard non-target species and maintain ecosystem health. Future research must prioritize comprehensive assessments of PPF's ecological impact across various habitats and taxa to inform evidence-based policymaking.

The role of neuropeptide prothoracicotropic hormone (PTTH) - Torso in pyriproxyfen-induced larval-pupal abnormal metamorphosis in silkworms

The neuropeptide prothoracicotropic hormone (PTTH) plays a key role in regulating ecdysone synthesis and promoting insect metamorphosis. Pyriproxyfen is a juvenile hormone analogue. We previously reported that pyriproxyfen disrupts ecdysone secretion and inhibits larval-pupal metamorphosis in silkworms. However, the specific molecular mechanisms by which pyriproxyfen interferes with ecdysone signaling remain to be elucidated. Herein, the RNA-seq analysis on the ecdysone-secretion organ prothoracic gland (PG) was conducted following pyriproxyfen exposure. A total of 3774 differentially expressed genes (DEGs) were identified, with 1667 up-regulated and 2107 down-regulated. KEGG analysis showed that DEGs were enriched in the MAPK signaling pathway, a conserved pathway activated by PTTH binding to Torso, which regulates the ecdysone synthesis. qRT-PCR results indicated a significant up-regulation in PTTH transcription level, while the transcription levels of torso and downstream MAPK pathway genes, Ras2, Raf and ERK, were down-regulated 24 h post-pyriproxyfen treatment. Consistent with these transcriptional changes, PTTH titers in the brain also increased following pyriproxyfen treatment. These results suggest that pyriproxyfen induces abnormal metamorphosis in silkworms by impairing PTTH-Torso signaling. This study enhances our understanding of the molecular mechanisms of pyriproxyfen-induced larval-pupal abnormal metamorphosis in silkworms, and also provides insights for developing detoxification strategies for juvenile hormone analog pesticides to non-target organisms.

Self-Assembled Nanoparticles of Silicon (IV)-NO Donor Phthalocyanine Conjugate for Tumor Photodynamic Therapy in Red Light

The combination of photodynamic therapy (PDT) and pneumatotherapy is emerging as one of the most effective strategies for increasing cancer treatment efficacy while minimizing side effects. Photodynamic forces affect nitric oxide (NO) levels as activated photosensitizers produce NO, and NO levels in the tumor and microenvironment directly impact tumor cell responsiveness to PDT. In this paper, 3-benzenesulfonyl-4-(1-hydroxy ether)-1,2,5-oxadiazole-2-oxide NO donor-silicon phthalocyanine coupling (SiPc-NO) was designed and prepared into self-assembled nanoparticles (SiPc-NO@NPs) by precipitation method. By further introducing arginyl-glycyl-aspartic acid (RGD) on the surface of nanoparticles, NO-photosensitizer delivery systems (SiPc-NO@RGD NPs) with photo-responsive and tumor-targeting properties were finally prepared and preliminarily evaluated in terms of their formulation properties, NO release, and photosensitizing effects. Furthermore, high reactive oxygen species (ROS) generation efficiency and high PDT efficiency in two breast cancer cell lines (human MCF-7 and mouse 4T1) under irradiation were also demonstrated. The novel SiPc-NO@RGD NPs show great potential for application in NO delivery and two-photon bioimaging-guided photodynamic tumor therapy.

The tissue-specific nature of physiological zebrafish mitochondrial bioenergetics

Zebrafish are a powerful tool to study a myriad of experimental conditions, including mitochondrial bioenergetics. Considering that mitochondria are different in many aspects depending on the tissue evaluated, in the zebrafish model there is still a lack of this investigation. Especially for juvenile zebrafish. In the present study, we examined whether different tissues from zebrafish juveniles show mitochondrial density- and tissue-specificity comparing brain, liver, heart, and skeletal muscle (SM). The liver and brain complex IV showed the highest O2 consumption of all ETC in all tissues (10x when compared to other respiratory complexes). The liver showed a higher potential for ROS generation. In this way, the brain and liver showed more susceptibility to O2- generation when compared to other tissues. Regarding Ca2+ transport, the brain showed greater capacity for Ca2+ uptake and the liver presented low Ca2+ uptake capacity. The liver and brain were more susceptible to producing NO. The enzymes SOD and Catalase showed high activity in the brain, whereas GPx showed higher activity in the liver and CS in the SM. TEM reveals, as expected, a physiological diverse mitochondrial morphology. The essential differences between zebrafish tissues investigated probably reflect how the mitochondria play a diverse role in systemic homeostasis. This feature may not be limited to normal metabolic functions but also to stress conditions. In summary, mitochondrial bioenergetics in zebrafish juvenile permeabilized tissues showed a tissue-specificity and a useful tool to investigate conditions of redox system imbalance, mainly in the liver and brain.

Assessment of toxicity of pyriproxyfen, Bacillus thuringiensis, and malathion and their mixtures used for mosquito control on embryo-larval development and behavior of zebrafish

Pyriproxyfen (PPF), Bacillus thuringiensis israelensis (BTI), and malathion (MLT) are widely used worldwide to control the population of mosquitos that transmit arboviruses. The current work aimed to evaluate the toxicity of these single pesticides and their binary mixtures of PPF + BTI, PPF + MLT, and MLT + BTI on the embryo-larval stage of zebrafish (Danio rerio) as an animal model. Epiboly, mortality, apical endpoints, affected animals, heart rate, morphometric, thigmotaxis, touch sensitivity, and optomotor response tests were evaluated. PPF and MLT and all mixtures reduced the epiboly percentage. Mortality increased significantly in all exposed groups, except BTI, with MLT being the most toxic. The observed apical endpoints were pericardial and yolk sac edemas, and tail and spine deformation. Exposure to MLT showed a higher percentage of affected animals. A reduction in heart rate was also observed in MLT- and PPF + MLT-exposed groups. The PPF + MLT mixture decreased head measurements. Behavioral alterations were observed, with a decrease in thigmotaxis and touch sensitivity responses in PPF + MLT and MLT + BTI groups. Finally, optomotor responses were affected in all groups. The above data obtained suggest that the MLT + PFF mixture has the greatest toxicity effects. This mixture affected embryo-larval development and behavior and is close to the reality in several cities that use both pesticides for mosquito control rather than single pesticides, leading to a reevaluation of the strategy for mosquito control.

Developmental toxicity of pyriproxyfen induces changes in the ultrastructure of neural cells and in the process of skull ossification

Some studies relate the use of pyriproxyfen (PPF) in drinking water with damage to embryonic neurodevelopment, including a supposed association with cases of microcephaly. However, the effects on neural cells and skull ossification in embryos remain unclear. This study aims to investigate the effects of PPF on the structure and ultrastructure of brain cells and its influence on the skull ossification process during embryonic development. Chicken embryos, used as an experimental model, were exposed to concentrations of 0.01 and 10 mg/l PPF at E1. The findings demonstrated that PPF led to notable ultrastructural alterations such as reduced cilia and microvilli of ependymal cells and damage to mitochondria, endoplasmic reticulum, Golgi bodies, and cell membranes in neural cells. The frequency of changes and the degree of these cell damage between the forebrain and midbrain were similar. PPF induced a reduction in fox3 transcript levels, specific for differentiation of neurons, and a reduction in the NeuN protein content related to mature neurons and dendritic branches. PPF impacted the ossification process of the skull, as evidenced by the increase in the ossified area and the decrease in inter-bone spacing. In conclusion, this study highlights the ability of PPF to affect neurodevelopmental processes by inducing ultrastructural damage to neural cells, concomitant with a reduction in NeuN and fox3 expression. This detrimental impact coupled with deficiencies in skull ossification can prevent the proper growth and development of the brain.

Embryotoxic Effects of Pesticides in Zebrafish (Danio rerio): Diflubenzuron, Pyriproxyfen, and Its Mixtures

Diflubenzuron (DFB) and pyriproxyfen (PPF) are larvicides used in crops to control insect plagues. However, these pesticides are known to impact non-target organisms like fish and mammals. Here, we aimed at assessing the embryotoxicity of purified DFB, PPF, and their mixtures in a non-target organism-zebrafish. Zebrafish embryos were exposed to different concentrations for 120 h: 0.025, 0.125, 0.25, 1.25, 2.5, and 10 mg/L of purified PPF and purified DFB, while we used 0.025 mg/L PPF + 10 mg/L DFB (Mix A), 0.125 mg/L PPF + 10 mg/L DFB (Mix B), and 0.25 mg/L PPF + 10 mg/L DFB (Mix C) for the mixtures of PPF + DFB. We observed mortality, teratogenicity, and cardiotoxicity. For the neurotoxicity tests and evaluation of reactive oxygen species (ROS) levels in the brain, embryos were exposed for 120 h to 0.379 and 0.754 mg/L of PPF and 0.025 and 0.125 mg/L of DFB. We established the LC50 for PPF as 3.79 mg/L, while the LC50 for DFB was not determinable. Survival and hatching were affected by PPF concentrations above 0.125 mg/L, DFB concentrations above 1.25 mg/L, and the lower pesticide mixtures. PPF exposure and mixtures induced different types of malformations, while a higher number of malformations were observed for the mixtures, suggesting a potentiating effect. Pesticides diminished avoidance responses and increased the levels of ROS across all concentrations, indicating neurotoxicity. Our findings underscore the detrimental impact of PPF and DFB exposure, spanning from biochemistry to morphology. There is a critical need to reconsider the global use of these pesticides and transition to more ecologically friendly forms of pest control, raising an alarm regarding repercussions on human and animal health and well-being.

Biochemical and teratogenic effects of a mixture of pyriproxyfen and glyphosate

The mixture of agrochemicals can be made to improve pest control or accidentally. In this way, the effects on non-target organisms are a critical aspect of the environment and heath. Thus, this work aimed to show how a mixture of pyriproxyfen, and glyphosate can impair biochemical routes and embryonic development. Zebrafish embryos 0-72 hpf were exposed to 0.001-1 μg/mL of pyriproxyfen, glyphosate, and a mixture of both pesticides. The ADMETox was evaluated in silico. The FET-test was used to estimate teratogenic effects. The biochemical effects were estimated using AChE, SOD, and CAT as parameters. ROS generation was estimated using 30 μM H2DCF-DA and 5 μM DHE. The ADMETox reveals that intestinal absorption and P-glycoprotein are the main sites for PPx and Gly adsorption. The distribution parameters were diverse. PPx + Gly at 0.1 μg/mL leads to 50 % of lethality and at 1 μg/mL 100 % of lethality. PPx + Gly leads to a 22 % of lack of somite formation at 1 μg/mL. The heart rate was reduced by >10 % in all concentrations tested. The AChE has a decrease with IC20 19.6 μM and IC50 261.5 μM. SOD showed a reduction of 28 % to PPx and CAT was reduced by 58 % to PPx + Gly and Gly at 1 μg/mL. Glyphosate does not increase unspecific ROS generation. The superoxide generation was 2× higher in the PPx + Gly at 1 μg/mL. Summarily, was observed that the mixture of PPx + Gly potentiated the toxic effects. This finding suggests a possible synergism between the PPx and Gly even at lower concentrations.

Histopathological and Behavioral Impairments in Zebrafish (Danio rerio) Chronically Exposed to a Cocktail of Fipronil and Pyriproxyfen

BACKGROUND

Lately, the high incidence of pesticide usage has attracted everyone's interest due to the serious effects produced. Fipronil (FIP) is a phenylpyrazole compound that acts on the insect's GABA neurotransmitter by inhibiting its activity. Moreover, the literature reports highlight its implication in neurodevelopmental abnormalities and oxidative stress production in different organisms. Similarly, pyriproxyfen (PYR) is known to affect insect activity by mimicking the natural hormones involved in the maturation of the young insects. The aim of the present study was to investigate the impact of the mixture of these pesticides on the tissues and behavior of zebrafish.

METHODS

To assess the influence of this cocktail on zebrafish, three groups of animals were randomly selected and exposed to 0, 0.05, and 0.1 mg L-1 FIP and PYR mixture for five days. The fish were evaluated daily by the T-maze tests for locomotor activity and the light-dark test and recordings lasted four min. The data were quantified using the EthoVision software.

RESULTS

Our results indicated significant changes in locomotor activity parameters that showed increased levels following exposure to the mixture of FIP and PYR. On the other hand, the mixture also triggered anxiety in the zebrafish, which spent more time in the light area than in the dark area. In addition, mixture-induced histological changes were observed in the form of numerous hemosiderin deposits found in various zebrafish tissues.

CONCLUSIONS

The current findings indicate that the mixture of FIP and PYR can have considerable consequences on adult zebrafish and may promote or cause functional neurological changes in addition to histological ones.

Impacts of Environmental Pollution on Brain Tumorigenesis

Pollutants consist of several components, known as direct or indirect mutagens, that can be associated with the risk of tumorigenesis. The increased incidence of brain tumors, observed more frequently in industrialized countries, has generated a deeper interest in examining different pollutants that could be found in food, air, or water supply. These compounds, due to their chemical nature, alter the activity of biological molecules naturally found in the body. The bioaccumulation leads to harmful effects for humans, increasing the risk of the onset of several pathologies, including cancer. Environmental components often combine with other risk factors, such as the individual genetic component, which increases the chance of developing cancer. The objective of this review is to discuss the impact of environmental carcinogens on modulating the risk of brain tumorigenesis, focusing our attention on certain categories of pollutants and their sources.

Pesticide contamination in agro-ecosystems: toxicity, impacts, and bio-based management strategies

Continuous rise in application of pesticides in the agro-ecosystems in order to ensure food supply to the ever-growing population is of greater concern to the human health and the environment. Once entered into the agro-ecosystem, the fate and transport of pesticides is determined largely by the nature of pesticides and the soil attributes, in addition to the soil-inhabiting microbes, fauna, and flora. Changes in the soil microbiological actions, soil properties, and enzymatic activities resulting from pesticide applications are the important factors substantially affecting the soil productivity. Disturbances in the microbial community composition may lead to the considerable perturbations in cycling of major nutrients, metals, and subsequent uptake by plants. Indiscriminate applications are linked with the accumulation of pesticides in plant-based foods, feeds, and animal products. Furthermore, rapid increase in the application of pesticides having long half-life has also been reported to contaminate the nearby aquatic environments and accumulation in the plants, animals, and microbes surviving there. To circumvent the negative consequences of pesticide application, multitude of techniques falling in physical, chemical, and biological categories are presented by different investigators. In the present study, important findings pertaining to the pesticide contamination in cultivated agricultural soils; toxicity on soil microbes, plants, invertebrates, and vertebrates; effects on soil characteristics; and alleviation of toxicity by bio-based management approaches have been thoroughly reviewed. With the help of bibliometric analysis, thematic evolution and research trends on the bioremediation of pesticides in the agro-ecosystems have also been highlighted.

The Role of Mitochondrial Enzymes, Succinate-Coupled Signaling Pathways and Mitochondrial Ultrastructure in the Formation of Urgent Adaptation to Acute Hypoxia in the Myocardium

The effect of a single one-hour exposure to three modes of hypobaric hypoxia (HBH) differed in the content of O₂ in inhaled air (FiO₂-14%, 10%, 8%) in the development of mitochondrial-dependent adaptive processes in the myocardium was studied in vivo. The following parameters have been examined: (a) an urgent reaction of catalytic subunits of mitochondrial enzymes (NDUFV2, SDHA, Cyt b, COX2, ATP5A) in the myocardium as an indicator of the state of the respiratory chain electron transport function; (b) an urgent activation of signaling pathways dependent on GPR91, HIF-1α and VEGF, allowing us to assess their role in the formation of urgent mechanisms of adaptation to hypoxia in the myocardium; (c) changes in the ultrastructure of three subpopulations of myocardial mitochondria under these conditions. The studies were conducted on two rat phenotypes: rats with low resistance (LR) and high resistance (HR) to hypoxia. The adaptive and compensatory role of the mitochondrial complex II (MC II) in maintaining the electron transport and energy function of the myocardium in a wide range of reduced O₂ concentrations in the initial period of hypoxic exposure has been established. The features of urgent reciprocal regulatory interaction of NAD- and FAD-dependent oxidation pathways in myocardial mitochondria under these conditions have been revealed. The data indicating the participation of GPR91, HIF-1a and VEGF in this process have been obtained. The ultrastructure of the mitochondrial subpopulations in the myocardium of LR and HR rats differed in normoxic conditions and reacted differently to hypoxia of varying severity. The parameters studied together are highly informative indicators of the quality of cardiac activity and metabolic biomarkers of urgent adaptation in various hypoxic conditions.

Toxicological effects of trace amounts of pyriproxyfen on the midgut of non-target insect silkworm

Pyriproxyfen is an insect growth regulator that is widely used in public health and pest control in agriculture. Our previous studies have shown that trace amounts of pyriproxyfen in the environment can cause serious toxic effects in the non-target insect silkworm, including failing to pupate, metamorphose and spin cocoons. However, it is unknown why pyriproxyfen not only has no lethal effects on fifth instar larvae but also tend to increase their body weight. The midgut is the main digestive organs of the silkworm, our results showed that the residual of pyriproxyfen in the silkworm at 24 h after 1 × 10^-4 mg/L pyriproxyfen treatment caused severe damage to the midgut microvilli, goblet cells, and nuclei of the silkworm, but body weight and digestibility of the larval were both increased. In addition, pyriproxyfen significantly (p < 0.05) increased the activities of digestive enzymes (α-amylase, trehalase, trypsin and lipase) in the midgut of silkworm. However, it caused down-regulation of ecdysone synthesis-related genes at the end of the fifth instar silkworm, decreased ecdysone titer, and prolonged larval instar. At the same time, pyriproxyfen also activated transcription of detoxification enzymes-related genes such as the cytochrome P450 enzyme genes Cyp9a22 and Cyp15C1, the carboxylesterase genes CarE-8 and CarE-11, and the glutathione S-transferase gene GSTo2. This study elucidated a novel toxicological effect of pyriproxyfen to insects, which not only expands the understanding of the effects of juvenile hormone pesticides on lepidopteran insects but also provides a reference for exploring the ecological security of non-target organisms.

Pesticide Pollution: Detrimental Outcomes and Possible Mechanisms of Fish Exposure to Common Organophosphates and Triazines

Pesticides are well known for their high levels of persistence and ubiquity in the environment, and because of their capacity to bioaccumulate and disrupt the food chain, they pose a risk to animals and humans. With a focus on organophosphate and triazine pesticides, the present review aims to describe the current state of knowledge regarding spatial distribution, bioaccumulation, and mode of action of frequently used pesticides. We discuss the processes by which pesticides and their active residues are accumulated and bioconcentrated in fish, as well as the toxic mechanisms involved, including biological redox activity, immunotoxicity, neuroendocrine disorders, and cytotoxicity, which is manifested in oxidative stress, lysosomal and mitochondrial damage, inflammation, and apoptosis/autophagy. We also explore potential research strategies to close the gaps in our understanding of the toxicity and environmental risk assessment of organophosphate and triazine pesticides.

Acetylcholinesterase from the charru mussel Mytella charruana: kinetic characterization, physicochemical properties and potential as in vitro biomarker in environmental monitoring of mollusk extraction areas

Acetylcholinesterase (AChE; EC 3.1.1.7) from aquatic organisms have been used to evaluate the exposure of specimens to pesticides and heavy metals at sublethal levels in environmental samples. AChE of Mytella charruana was extracted to characterize its physicochemical and kinetic properties as well as the effect of organophosphate (dichlorvos, diazinon, chlorpyrifos, methyl-parathion and temephos), carbamates (carbaryl, carbofuran and aldicarb), benzoylureas (diflubenzuron and novaluron), pyrethroid (cypermethrin) and juvenile hormone analog - JHA (pyriproxyfen) and the effect of metal ions: Hg²⁺, Cd²⁺, Pb²⁺, As³⁺, Cu²⁺ and Zn²⁺, in order to evaluate the potential of the enzyme as biomarker. The optimum pH of M. charruana AChE was 8.5 and the maximum activity peak occurred at 48 °C, being highly thermostable maintaining 97.8% of its activity after incubation at 60 °C. The Michaelis-Menten constants (k_m) for the substrates acetylthiocholine and propionylthiocholine were 2.8 ± 1.26 and 4.94 ± 6.9 mmol·L^-1, respectively. The V_max values for the same substrates were 22.6 ± 0.90 and 10.2 ± 4.94 mU·mg^-1, respectively. Specific inhibition results suggest an AChE presenting active site with dimensions between those of AChE and butyrylcholinesterase (BChE). The IC₂₀ values related to the effect of the pesticides on the enzyme showed higher inhibitory power of temephos (0.17 μmol·L^-1), followed by aldicarb (0.19 μmol·L^-1) and diflubenzuron (0.23 μmol·L^-1). Metal ions inhibited M. charruana enzyme in the following order: Hg²⁺ > Pb²⁺ > Cd²⁺ > As³⁺ > Cu²⁺ > Zn²⁺. These data suggest that the enzyme showed potential as in vitro biomarker of the exposure to temephos, mercury, zinc and copper.

Midgut and fat body: Multisystemic action of pyriproxyfen on non-target organism Ceraeochrysa claveri (Neuroptera: Chrysopidae)

Morphological tools can assist in the evaluation of effects of insecticides on non-target insects. Pyriproxyfen, a juvenile hormone analog, is known to interfere with growth and metamorphosis of insects. However, there are studies showing indirect effects on natural enemies, including green lacewings. Few prior studies describe morphological effects of pyriproxyfen on target insect organs, especially on natural enemies. Through morphological tools, this study aimed to characterize the midgut and fat body, both important organs of digestion and great metabolic activity respectively, of the predator Ceraeochrysa claveri after chronic exposure to pyriproxyfen. Larvae of C. claveri were fed Diatraea saccharalis egg clusters treated with pyriproxyfen in solution of 50 or 100 mg a.i. L^-1 throughout the larval stage. The biological data revealed significant increases in development time, especially in the third instar, and in cumulative mortality from the prepupal into the pupal stage. Morphological analysis of adult midgut (≤24 h old) showed damage including formation of epithelial folds, intercellular spaces, emission of cytoplasmic protrusions. Both fat body regions presented decrease of lipid droplets, vacuolization of trophocytes and mitochondrial injury featuring a multisystemic action. In both organs, pyriproxyfen exposure induced significant oxidative stress by mitochondrial superoxide production. Cytoprotective responses were induced in midgut and fat body cells by augmenting the number of cytoplasmic granules containing calcium and expression of HSP 90. Both organs proved to be efficient in presenting histopathological alterations, showing the sensitivity and applicability of this morphological tool for evaluating other insecticides in non-target organisms.

Systematic Review of Calcium Channels and Intracellular Calcium Signaling: Relevance to Pesticide Neurotoxicity

Pesticides of different chemical classes exert their toxic effects on the nervous system by acting on the different regulatory mechanisms of calcium (Ca2+) homeostasis. Pesticides have been shown to alter Ca2+ homeostasis, mainly by increasing its intracellular concentration above physiological levels. The pesticide-induced Ca2+ overload occurs through two main mechanisms: the entry of Ca2+ from the extracellular medium through the different types of Ca2+ channels present in the plasma membrane or its release into the cytoplasm from intracellular stocks, mainly from the endoplasmic reticulum. It has also been observed that intracellular increases in the Ca2+ concentrations are maintained over time, because pesticides inhibit the enzymes involved in reducing its levels. Thus, the alteration of Ca2+ levels can lead to the activation of various signaling pathways that generate oxidative stress, neuroinflammation and, finally, neuronal death. In this review, we also discuss some proposed strategies to counteract the detrimental effects of pesticides on Ca2+ homeostasis.

Impact on cholinesterase-inhibition and in silico investigations of sesquiterpenoids from Amazonian Siparuna guianensis Aubl

The plant popularly known as "negramina" (Siparuna guianensis Aubl.), member of the family Siparunaceae produces an essential oil that presents several biological activities reported in literature. Here, the essential oil was obtained by hydrodistillation from fresh leaves collected in the state of Roraima, far north of the Amazon. Chemical composition of the essential oil was characterized by gas chromatography coupled to mass spectrometry (GC-MS) and flame ionization detector (GC-FID). The sesquiterpenoid shyobunone and its derivatives were identified as major compounds in the oil (>40%). The effect of S. guianensis essential oil on the acetylcholinesterase (AChE) activity from Crassostrea rhizophorae, Litopenaeus vannamei and Electrophorus electricus was tested by spectrophotometric assays. The essential oil has been identified as an AChE inhibitor. The mechanism of inhibition was investigated as well as spectrofluorimetric interactions between the essential oil and the enzyme. ¹H NMR titration and molecular docking were also investigated. The spectrophotometric results revealed that shyobunone and its derivatives strongly interact with AChE with a kind of non-competitive inhibition. Interaction studies support the results of enzyme inhibition. Molecular coupling predicted that iso-shyobunone is the strongest ligand, corroborated by fluorescence suppression and ¹H NMR titration results. In conclusion, Siparuna guianensis essential oil can be a new source of shyobunone and derivatives capable to reversibly inhibit AChE showing potential neuroprotective properties to be applied in the treatment of Alzheimer's disease.