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1.
Int J Mol Sci ; 22(23)2021 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-34884838

RESUMO

Alterations to amino acid residues G4946 and I4790, associated with resistance to diamide insecticides, suggests a location of diamide interaction within the pVSD voltage sensor-like domain of the insect ryanodine receptor (RyR). To further delineate the interaction site(s), targeted alterations were made within the same pVSD region on the diamondback moth (Plutella xylostella) RyR channel. The editing of five amino acid positions to match those found in the diamide insensitive skeletal RyR1 of humans (hRyR1) in order to generate a human-Plutella chimeric construct showed that these alterations strongly reduce diamide efficacy when introduced in combination but cause only minor reductions when introduced individually. It is concluded that the sites of diamide interaction on insect RyRs lie proximal to the voltage sensor-like domain of the RyR and that the main site of interaction is at residues K4700, Y4701, I4790 and S4919 in the S1 to S4 transmembrane domains.


Assuntos
Diamida/química , Proteínas de Insetos/química , Canal de Liberação de Cálcio do Receptor de Rianodina/química , Animais , Sítios de Ligação , Cafeína/farmacologia , Sinalização do Cálcio/efeitos dos fármacos , Diamida/metabolismo , Diamida/farmacologia , Humanos , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Resistência a Inseticidas/efeitos dos fármacos , Inseticidas/química , Inseticidas/metabolismo , Inseticidas/farmacologia , Mariposas/metabolismo , Mutagênese Sítio-Dirigida , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , ortoaminobenzoatos/química , ortoaminobenzoatos/metabolismo , ortoaminobenzoatos/farmacologia
2.
Pestic Biochem Physiol ; 167: 104587, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32527435

RESUMO

Insecticide resistance has been and continues to be a significant problem for invertebrate pest control. As such, effective insecticide resistance management (IRM) is critical to maintain the efficacy of current and future insecticides. A technical group within CropLife International, the Insecticide Resistance Action Committee (IRAC) was established 35 years ago (1984) as an international association of crop protection companies that today spans the globe. IRAC's focus is on preserving the long-term utility of insect, mite, and most recently nematode control products through effective resistance management to promote sustainable agriculture and improved public health. A central task of IRAC has been the continual development and documentation of the Mode of Action (MoA) Classification scheme, which serves as an important tool for implementing IRM strategies focused on compound rotation / alternations. Updates to the IRAC MoA Classification scheme provide the latest information on the MoA of current and new insecticides and acaricides, and now includes information on biologics and nematicides. Details for these new changes and additions are reviewed herein.


Assuntos
Produtos Biológicos , Inseticidas , Animais , Antinematódeos , Insetos , Resistência a Inseticidas
3.
Pest Manag Sci ; 78(3): 869-880, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34821007

RESUMO

BACKGROUND: Resistance to diamide insecticides in Lepidoptera is known to be caused primarily by amino acid changes on the ryanodine receptor (RyR). Recently, two new target site mutations, G4946V and I4790M, have emerged in populations of diamondback moth, Plutella xylostella, as well as in other lepidopteran species, and both mutations have been shown empirically to decrease diamide efficacy. Here, we quantify the impact of the I4790M mutation on diamide activation of the receptor, as compared to alterations at the G4946 locus. RESULTS: I4790M when introduced into P. xylostella RyR expressed in an insect-derived Sf9 cell line was found to mediate just a ten-fold reduction in chlorantraniliprole efficacy (compared to 104- and 146-fold reductions for the G4946E and G4946V variants, respectively), whilst in the field its presence is associated with a ≥150-fold reduction. I4790M-mediated resistance to flubendiamide was estimated to be >24-fold. When the entire coding sequence of P. xylostella RyR was integrated into Drosophila melanogaster, the I4790M variant conferred ~4.4-fold resistance to chlorantraniliprole and 22-fold resistance to flubendiamide in the 3rd instar larvae, confirming that it imparts only a moderate level of resistance to diamide insecticides. Although the I4790M substitution appears to bear no fitness costs in terms of the flies' reproductive capacity, when assessed in a noncompetitive environment, it does, however, have potentially major impacts on mobility at both the larval and adult stages. CONCLUSIONS: I4790M imparts only a moderate level of resistance to diamide insecticides and potentially confers significant fitness costs to the insect.


Assuntos
Resistência a Inseticidas , Mariposas , Canal de Liberação de Cálcio do Receptor de Rianodina , Animais , Animais Geneticamente Modificados , Linhagem Celular , Diamida/farmacologia , Drosophila melanogaster/genética , Resistência a Inseticidas/genética , Mariposas/genética , Mutação , Canal de Liberação de Cálcio do Receptor de Rianodina/genética
4.
Artigo em Inglês | MEDLINE | ID: mdl-35284893

RESUMO

Malaria vector control interventions rely heavily on the application of insecticides against anopheline mosquitoes, in particular the fast-acting pyrethroids that target insect voltage-gated sodium channels (VGSC). Frequent applications of pyrethroids have resulted in resistance development in the major malaria vectors including Anopheles funestus, where resistance is primarily metabolic and driven by the overexpression of microsomal cytochrome P450 monooxygenases (P450s). Here we examined the pattern of cross-resistance of the pyrethroid-resistant An. funestus strain FUMOZ-R towards transfluthrin and multi-halogenated benzyl derivatives, permethrin, cypermethrin and deltamethrin in comparison to the susceptible reference strain FANG. Transfluthrin and two multi-fluorinated derivatives exhibited micromolar potency - comparable to permethrin - to functionally expressed dipteran VGSC in a cell-based cation influx assay. The activity of transfluthrin and its derivatives on VGSC was strongly correlated with their contact efficacy against strain FUMOZ-R, although no such correlation was obtained for the other pyrethroids due to their rapid detoxification by the resistant strain. The low resistance levels for transfluthrin and derivatives in strain FUMOZ-R were only weakly synergized by known P450 inhibitors such as piperonyl butoxide (PBO), triflumizole and 1-aminobenzotriazole (1-ABT). In contrast, deltamethrin toxicity in FUMOZ-R was synergized > 100-fold by all three P450 inhibitors. The biochemical profiling of a range of fluorescent resorufin and coumarin compounds against FANG and FUMOZ-R microsomes identified 7-benzyloxymethoxy-4-trifluoromethylcoumarin (BOMFC) as a highly sensitive probe substrate for P450 activity. BOMFC was used to develop a fluorescence-based high-throughput screening assay to measure the P450 inhibitory action of potential synergists. Azole fungicides prochloraz and triflumizole were identified as extremely potent nanomolar inhibitors of microsomal P450s, strongly synergizing deltamethrin toxicity in An. funestus. Overall, the present study contributed to the understanding of transfluthrin efficacy at the molecular and organismal level and identified azole compounds with potential to synergize pyrethroid efficacy in malaria vectors.

5.
Nat Commun ; 12(1): 7164, 2021 12 09.
Artigo em Inglês | MEDLINE | ID: mdl-34887422

RESUMO

Slowpoke (Slo) potassium channels display extraordinarily high conductance, are synergistically activated by a positive transmembrane potential and high intracellular Ca2+ concentrations and are important targets for insecticides and antiparasitic drugs. However, it is unknown how these compounds modulate ion translocation and whether there are insect-specific binding pockets. Here, we report structures of Drosophila Slo in the Ca2+-bound and Ca2+-free form and in complex with the fungal neurotoxin verruculogen and the anthelmintic drug emodepside. Whereas the architecture and gating mechanism of Slo channels are conserved, potential insect-specific binding pockets exist. Verruculogen inhibits K+ transport by blocking the Ca2+-induced activation signal and precludes K+ from entering the selectivity filter. Emodepside decreases the conductance by suboptimal K+ coordination and uncouples ion gating from Ca2+ and voltage sensing. Our results expand the mechanistic understanding of Slo regulation and lay the foundation for the rational design of regulators of Slo and other voltage-gated ion channels.


Assuntos
Calpaína/química , Calpaína/metabolismo , Proteínas de Drosophila/química , Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Animais , Anti-Helmínticos/química , Anti-Helmínticos/farmacologia , Transporte Biológico , Cálcio/metabolismo , Calpaína/genética , Microscopia Crioeletrônica , Depsipeptídeos/química , Depsipeptídeos/farmacologia , Drosophila/efeitos dos fármacos , Drosophila/genética , Drosophila/ultraestrutura , Proteínas de Drosophila/genética , Indóis/química , Indóis/farmacologia , Potássio/metabolismo
6.
Cell Calcium ; 39(1): 21-33, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16219348

RESUMO

Flubendiamide represents a novel chemical family of substituted phthalic acid diamides with potent insecticidal activity. So far, the molecular target and the mechanism of action were not known. Here we present for the first time evidence that phthalic acid diamides activate ryanodine-sensitive intracellular calcium release channels (ryanodine receptors, RyR) in insects. With Ca(2+) measurements, we showed that flubendiamide and related compounds induced ryanodine-sensitive cytosolic calcium transients that were independent of the extracellular calcium concentration in isolated neurons from the pest insect Heliothis virescens as well as in transfected CHO cells expressing the ryanodine receptor from Drosophila melanogaster. Binding studies on microsomal membranes from Heliothis flight muscles revealed that flubendiamide and related compounds interacted with a site distinct from the ryanodine binding site and disrupted the calcium regulation of ryanodine binding by an allosteric mechanism. This novel insecticide mode of action seems to be restricted to specific RyR subtypes because the phthalic acid diamides reported here had almost no effect on mammalian type 1 ryanodine receptors.


Assuntos
Cálcio/metabolismo , Diamida/farmacologia , Mariposas/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/efeitos dos fármacos , Rianodina/metabolismo , Animais , Benzamidas/farmacologia , Células CHO , Cafeína/farmacologia , Linhagem Celular , Cricetinae , Citosol/metabolismo , Drosophila melanogaster , Fura-2 , Membranas Intracelulares/química , Compostos Macrocíclicos , Camundongos , Microscopia de Fluorescência , Músculos/química , Músculos/metabolismo , Neurônios/metabolismo , Oxazóis/farmacologia , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Sulfonas/farmacologia , Transfecção
7.
Pest Manag Sci ; 71(6): 850-62, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25351824

RESUMO

BACKGROUND: The development and commercialisation of new chemical classes of insecticides for efficient crop protection measures against destructive invertebrate pests is of utmost importance to overcome resistance issues and to secure sustainable crop yields. Flupyradifurone introduced here is the first representative of the novel butenolide class of insecticides active against various sucking pests and showing an excellent safety profile. RESULTS: The discovery of flupyradifurone was inspired by the butenolide scaffold in naturally occurring stemofoline. Flupyradifurone acts reversibly as an agonist on insect nicotinic acetylcholine receptors but is structurally different from known agonists, as shown by chemical similarity analysis. It shows a fast action on a broad range of sucking pests, as demonstrated in laboratory bioassays, and exhibits excellent field efficacy on a number of crops with different application methods, including foliar, soil, seed treatment and drip irrigation. It is readily taken up by plants and translocated in the xylem, as demonstrated by phosphor imaging analysis. Flupyradifurone is active on resistant pests, including cotton whiteflies, and is not metabolised by recombinantly expressed CYP6CM1, a cytochrome P450 conferring metabolic resistance to neonicotinoids and pymetrozine. CONCLUSION: The novel butenolide insecticide flupyradifurone shows unique properties and will become a new tool for integrated pest management around the globe, as demonstrated by its insecticidal, ecotoxicological and safety profile.


Assuntos
4-Butirolactona/análogos & derivados , Afídeos , Hemípteros , Inseticidas , Agonistas Nicotínicos , Piridinas , 4-Butirolactona/química , 4-Butirolactona/toxicidade , Animais , Produtos Agrícolas , Resistência a Inseticidas , Inseticidas/química , Inseticidas/toxicidade , Agonistas Nicotínicos/química , Agonistas Nicotínicos/toxicidade , Piridinas/química , Piridinas/toxicidade
8.
PLoS Negl Trop Dis ; 9(10): e0004062, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26437177

RESUMO

The anthelmintic emodepside paralyses adult filarial worms, via a mode of action distinct from previous anthelmintics and has recently garnered interest as a new treatment for onchocerciasis. Whole organism data suggest its anthelmintic action is underpinned by a selective activation of the nematode isoform of an evolutionary conserved Ca2+-activated K+ channel, SLO-1. To test this at the molecular level we compared the actions of emodepside at heterologously expressed SLO-1 alpha subunit orthologues from nematode (Caenorhabditis elegans), Drosophila melanogaster and human using whole cell voltage clamp. Intriguingly we found that emodepside modulated nematode (Ce slo-1), insect (Drosophila, Dm slo) and human (hum kcnma1)SLO channels but that there are discrete differences in the features of the modulation that are consistent with its anthelmintic efficacy. Nematode SLO-1 currents required 100 µM intracellular Ca2+ and were strongly facilitated by emodepside (100 nM; +73.0 ± 17.4%; n = 9; p < 0.001). Drosophila Slo currents on the other hand were activated by emodepside (10 µM) in the presence of 52 nM Ca2+ but were inhibited in the presence of 290 nM Ca2+ and exhibited a characteristic loss of rectification. Human Slo required 300 nM Ca2+ and emodepside transiently facilitated currents (100 nM; +33.5 ± 9%; n = 8; p<0.05) followed by a sustained inhibition (-52.6 ± 9.8%; n = 8; p < 0.001). This first cross phyla comparison of the actions of emodepside at nematode, insect and human channels provides new mechanistic insight into the compound's complex modulation of SLO channels. Consistent with whole organism behavioural studies on C. elegans, it indicates its anthelmintic action derives from a strong activation of SLO current, not observed in the human channel. These data provide an important benchmark for the wider deployment of emodepside as an anthelmintic treatment.


Assuntos
Anti-Helmínticos/farmacologia , Depsipeptídeos/farmacologia , Subunidades alfa do Canal de Potássio Ativado por Cálcio de Condutância Alta/efeitos dos fármacos , Animais , Células CHO , Cálcio/metabolismo , Cricetulus , Drosophila melanogaster , Células HEK293 , Humanos , Subunidades alfa do Canal de Potássio Ativado por Cálcio de Condutância Alta/antagonistas & inibidores , Subunidades Proteicas
9.
Parasit Vectors ; 5: 73, 2012 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-22498105

RESUMO

BACKGROUND: The control of tick and flea burdens in dogs and cats has become essential to the control of important and emerging vector borne diseases, some of which are zoonoses. Flea worry and flea bite hypersensitivity are additionally a significant disease entity in dogs and cats. Owner compliance in maintaining the pressure of control measures has been shown to be poor. For these reasons efforts are continuously being made to develop ectoparasiticides and application methods that are safe, effective and easy to apply for pet owners. A new polymer matrix collar has recently been developed which is registered for 8 months use in cats and dogs. The basic properties of this collar have been investigated in several in vitro and in vivo studies. METHODS: The effects of imidacloprid, flumethrin and the combination were evaluated in vitro by means of whole cell voltage clamp measurement experiments conducted on isolated neuron cells from Spodoptera frugiperda. The in vitro efficacy of the two compounds and the combination against three species of ticks and their life stages and fleas were evaluated in a dry surface glass vial assay. The kinetics of the compounds over time in the collar were evaluated by the change in mass of the collar and measurement of the surface concentrations and concentrations of the actives in the collar matrix by HPLC. Hair clipped from collar treated dogs and cats, collected at various time points, was used to assess the acaricidal efficacy of the actives ex vivo. RESULTS: An in vitro isolated insect nerve model demonstrated the synergistic neurotoxic effects of the pyrethroid flumethrin and the neonicotinoid imidacloprid. An in vitro glass vial efficacy and mortality study against various life stages of the ticks Ixodes ricinus, Rhipicephalus sanguineus and Dermacentor reticulatus and against the flea (Ctenocephalides felis) demonstrated that the combination of these products was highly effective against these parasites. The release kinetics of these actives from a neck collar (compounded with 10% imidacloprid and 4.5% flumethrin) was extensively studied in dogs and cats under laboratory and field conditions. Acaricidal concentrations of the actives were found to be consistently released from the collar matrix for 8 months. None of the collar studies in dogs or cats were associated with any significant collar related adverse event. CONCLUSION: Here we demonstrated the synergism between the pyrethroid flumethrin and the neonicotinoid imidacloprid, both provided in therapeutically relevant doses by a slow release collar matrix system over 8 months. This collar is therefore a convenient and safe tool for a long-term protection against ectoparasites.


Assuntos
Sistemas de Liberação de Medicamentos , Sinergismo Farmacológico , Imidazóis/farmacologia , Nitrocompostos/farmacologia , Piretrinas/farmacologia , Sifonápteros/efeitos dos fármacos , Carrapatos/efeitos dos fármacos , Animais , Doenças do Gato/prevenção & controle , Gatos , Doenças do Cão/prevenção & controle , Cães , Ectoparasitoses/prevenção & controle , Ectoparasitoses/veterinária , Feminino , Imidazóis/farmacocinética , Inseticidas/farmacocinética , Inseticidas/farmacologia , Masculino , Neonicotinoides , Nitrocompostos/farmacocinética , Piretrinas/farmacocinética
10.
J Nat Prod ; 71(1): 112-6, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18163592

RESUMO

Five new alkaloids, 6beta-hydroxystemofoline (1), 16-hydroxystemofoline (2), neostemofoline (3), protostemodiol (4), and 13-demethoxy-11(S*),12(R*)-dihydroprotostemonine (5), along with 10 known alkaloids, were isolated from stems and leaves of Stemona japonica. Their structures were elucidated by 1D and 2D NMR and other spectroscopic studies. The insecticidal activity of the agonist 16-hydroxystemofoline (2) and antagonist 13-demethoxy-11(S*),12(R*)-dihydroprotostemonine (5) was demonstrated by electrophysiological in vitro tests on the insect nicotinic acetylcholine receptor and by in vivo screenings against relevant agricultural insect pests.


Assuntos
Alcaloides/isolamento & purificação , Alcaloides/farmacologia , Afídeos/efeitos dos fármacos , Medicamentos de Ervas Chinesas/isolamento & purificação , Medicamentos de Ervas Chinesas/farmacologia , Inseticidas/isolamento & purificação , Inseticidas/farmacologia , Plantas Medicinais/química , Spodoptera/efeitos dos fármacos , Stemonaceae/química , Alcaloides/química , Animais , Brassica/efeitos dos fármacos , Medicamentos de Ervas Chinesas/química , Inseticidas/química , Estrutura Molecular , Folhas de Planta/química , Caules de Planta/química
11.
J Biol Chem ; 280(16): 16254-62, 2005 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-15713676

RESUMO

A systematic analysis of the Drosophila genome data reveals the existence of pHCl, a novel member of ligand-gated ion channel subunits. pHCl shows nearly identical similarity to glutamate-, glycine-, and histamine-gated ion channels, does however not belong to any of these ion channel types. We identified three different sites, where splicing generates multiple transcripts of the pHCl mRNA. The pHCl is expressed in Drosophila embryo, larvae, pupae, and the adult fly. In embryos, in situ hybridization detected pHCl in the neural cord and the hindgut. Functional expression of the three different splice variants of pHCl in oocytes of Xenopus laevis and Sf9 cells induces a chloride current with a linear current-voltage relationship that is inhibited by extracellular protons and activated by avermectins in a pH-dependent manner. Further, currents through pHCl channels were induced by a raise in temperature. Our data give genetic and electrophysiological evidence that pHCl is a member of a new branch of ligand-gated ion channels in invertebrates with, however, a hitherto unique combination of pharmacological and biophysical properties.


Assuntos
Canais de Cloreto/metabolismo , Drosophila melanogaster/metabolismo , Processamento Alternativo , Sequência de Aminoácidos , Animais , Células Cultivadas , Canais de Cloreto/genética , Drosophila melanogaster/embriologia , Drosophila melanogaster/genética , Larva/metabolismo , Potenciais da Membrana/fisiologia , Dados de Sequência Molecular , Oócitos , Prótons , Pupa/metabolismo , Spodoptera , Xenopus
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