Transmembrane potential polarization, calcium influx, and receptor conformational state modulate the sensitivity of the imidacloprid-insensitive neuronal insect nicotinic acetylcholine receptor to neonicotinoid insecticides

Neonicotinoid insecticides act selectively on insect nicotinic acetylcholine receptors (nAChRs). Recent studies revealed that their efficiency was altered by the phosphorylation/dephosphorylation process and the intracellular signaling pathway involved in the regulation of nAChRs. Using whole-cell patch-clamp electrophysiology adapted for dissociated cockroach dorsal unpaired median (DUM) neurons, we demonstrated that intracellular factors involved in the regulation of nAChR function modulated neonicotinoid sensitivity. DUM neurons were known to express two alpha-bungarotoxin-insensitive nAChR subtypes: nAChR1 and nAChR2. Whereas nAChR1 was sensitive to imidacloprid, nAChR2 was insensitive to this insecticide. Here, we demonstrated that, like nicotine, acetamiprid and clothianidin, other types of neonicotinoid insecticides, acted as agonists on the nAChR2 subtype. Using acetamiprid, we revealed that both steady-state depolarization and hyperpolarization affected nAChR2 sensitivity. The measurement of the input membrane resistance indicated that change in the acetamiprid-induced agonist activity was related to the receptor conformational state. Using cadmium chloride, omega-conotoxin GVIA, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-acetamide (LOE 908), we found that inhibition of calcium influx through high voltage-activated calcium channels and transient receptor potential gamma (TRPgamma) activated by both depolarization and hyperpolarization increased nAChR2 sensitivity to acetamiprid. Finally, using N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7), forskolin, and cAMP, we demonstrated that adenylyl cyclase sensitive to the calcium/calmodulin complex regulated internal cAMP concentration, which in turn modulated TRPgamma function and nAChR2 sensitivity to acetamiprid. Similar TRPgamma-induced modulatory effects were also obtained when clothianidin was tested. These findings bring insights into the signaling pathway modulating neonicotinoid efficiency and open novel strategies for optimizing insect pest control

Inhibition of PaCaMKII-E isoform in the dorsal unpaired median neurosecretory cells of cockroach reduces nicotine- and clothianidin-induced currents

Cellular responses to Ca(2+) require intermediary proteins such as calcium/calmodulin-dependent protein kinase II (CaMKII), which transduces the signal into downstream effects. We recently demonstrated that the cockroach genome encodes five different CaMKII isoforms, and only PaCaMKII-E isoform is specifically expressed in the dorsal unpaired median neurosecretory cells. In the present study, using antisense oligonucleotides, we demonstrated that PaCaMKII-E isoform inhibition reduced nicotine-induced currents through alpha-bungarotoxin-sensitive and -insensitive nicotinic acetylcholine receptor subtypes. Specifically, PaCaMKII-E isoform is sufficient to repress nicotinic current amplitudes as a result of its depression by antisense oligonucleotides. Similar results were found using the neonicotinoid insecticide clothianidin, which acted as a full agonist of dorsal unpaired median neuron nicotinic acetylcholine receptors. Clothianidin current amplitudes are strongly reduced under bath application of PaCaMKII-E antisense oligonucleotides but no significant results are found with alpha-bungarotoxin co-applied, demonstrating that CaMKII-E isoform affects nicotine currents through alpha-bungarotoxin-sensitive and -insensitive receptor subtypes whereas clothianidin currents are reduced via alpha-bungarotoxin-insensitive receptors. In addition, we found that intracellular calcium increase induced by nicotine and clothianidin were reduced by PaCaMKII-E antisense oligonucleotides, demonstrating that intracellular calcium increase induced by nicotine and clothianidin are affected by PaCaMKII-E inhibition. Cellular responses to Ca(2+) require intermediary proteins such as calcium/calmodulin-dependent protein kinase II (CaMKII). We recently demonstrated that the cockroach genome encodes five different CaMKII isoforms and only PaCaMKII-E isoform was specifically expressed in the dorsal unpaired median neurosecretory cells. Here we show that specific inhibition of PaCaMKII-E isoform is associated with a decrease in nicotine- and clothianidin-induced currents. In addition, analysis of calcium changes demonstrates that PaCaMKII-E inhibition induces a decrease in intracellular calcium concentration

Nornicotine application on cockroach dorsal unpaired median neurons induces two distinct ionic currents: implications of different nicotinic acetylcholine receptors

The goal of the present study is to examine the agonist action of nornicotine on insect nicotinic acetylcholine receptors. Using patch-clamp techniques on cockroach dorsal unpaired median neurons, we demonstrated that nornicotine induced two distinct ionic currents named types 1 and 2. We found that alpha-bungarotoxin induced a rapid desensitization of type 1 currents whereas type 2 was completely blocked. Interestingly, types 1 and 2 currents were not blocked by the muscarinic antagonist, pirenzepine but by co-application of 1 muM pirenzepine and 0.5 muM alpha-bungarotoxin, suggesting that muscarinic receptors modulated nornicotine-induced current amplitudes. In addition, type 1 current amplitudes were strongly reduced by 20 muM d-tubocurarine and 5 muM mecamylamine which blocked the previously identified alpha-bungarotoxin-insensitive nAChR1 and nAChR2 receptors. Co-application of alpha-bungarotoxin with d-tubocurarine or mecamylamine completely blocked all ionic currents. We propose that types 1 and 2 currents are associated to several nicotinic receptors subtypes, including nAChR1 and nAChR2 receptors. Finally, we conclude that nornicotine could be used as an agonist to identify distinct insect nicotinic receptors

Injection of insect membrane in Xenopus oocyte: An original method for the pharmacological characterization of neonicotinoid insecticides

Insect nicotinic acetylcholine receptors (nAChRs) represent a major target of insecticides, belonging to the neonicotinoid family. However, the pharmacological profile of native nAChRs is poorly documented, mainly because of a lack of knowledge of their subunit stoichiometry, their tissue distribution and the weak access to nAChR-expressing cells. In addition, the expression of insect nAChRs in heterologous systems remains hard to achieve. Therefore, the structure–activity characterization of nAChR-targeting insecticides is made difficult. The objective of the present study was to characterize insect nAChRs by an electrophysiological approach in a heterologous system naturally devoid of these receptors to allow a molecular/cellular investigation of the mode of action of neonicotinoids

Design of Pre-Dumping Ring Spin Rotator with a Possibility of Helicity Switching for Polarized Positrons at the ILC

The use of polarized beams enhance the possibility of the precision measurements at the International Linear Collider (ILC). In order to preserve the degree of polarization during beam transport spin rotators are included in the current TDR ILC Lattice. In this report some advantages of using a combined spin rotator/spin flipper are discussed. A few possible lattice designs of spin flipper developed at DESY in 2012 are presented.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201

The Delphi and GRADE methodology used in the PSOGI 2018 consensus statement on Pseudomyxoma Peritonei and Peritoneal Mesothelioma

Pseudomyxoma Peritonei (PMP) and Peritoneal Mesothelioma (PM) are both rare peritoneal malignancies. Currently, affected patients may be treated with Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy offering long-term survival or even cure in selected patients. However, many issues regarding the optimal treatment strategy are currently under debate. To aid physicians involved in the treatment of these patients in clinical decision making, the PSOGI executive committee proposed to create a consensus statement on PMP and PM. This manuscript describes the methodology of the consensus process. The Delphi technique is a reliable method for attaining consensus on a topic that lacks scientific evidence through multiple voting rounds which feeds back responses to the participants in between rounds. The GRADE system provides a structured framework for presenting and grading the available evidence. Separate questionnaires were created for PMP and PM and sent during two voting rounds to 80 and 38 experts, respectively. A consensus threshold of 51.0% was chosen. After the second round, consensus was reached on 92.9%–100.0% of the questions. The results were presented and discussed in the plenary session at the PSOGI 2018 international meeting in Paris. A third round for the remaining issues is currently in progress. In conclusion, using the Delphi technique and GRADE methodology, consensus was reached in many issues regarding the treatment of PM and PMP amongst an international panel of experts. The main results will be published in the near future