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Le Mauff A, Norris EJ, Li AY, Swale DR. Repellent activity of essential oils to the Lone Star tick, Amblyomma americanum. Parasit Vectors 2024; 17:202. [PMID: 38711138 DOI: 10.1186/s13071-024-06246-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 03/14/2024] [Indexed: 05/08/2024] Open
Abstract
BACKGROUND The Lone Star tick, Amblyomma americanum is important to human health because of a variety of pathogenic organisms transmitted to humans during feeding events, which underscores the need to identify novel approaches to prevent tick bites. Thus, the goal of this study was to test natural and synthetic molecules for repellent activity against ticks in spatial, contact and human fingertip bioassays. METHODS The efficacy of essential oils and naturally derived compounds as repellents to Am. americanum nymphs was compared in three different bioassays: contact, spatial and fingertip repellent bioassays. RESULTS Concentration response curves after contact exposure to 1R-trans-chrysanthemic acid (TCA) indicated a 5.6 μg/cm2 concentration required to repel 50% of ticks (RC50), which was five- and sevenfold more active than DEET and nootkatone, respectively. For contact repellency, the rank order of repellency at 50 μg/cm2 for natural oils was clove > geranium > oregano > cedarwood > thyme > amyris > patchouli > citronella > juniper berry > peppermint > cassia. For spatial bioassays, TCA was approximately twofold more active than DEET and nootkatone at 50 μg/cm2 but was not significantly different at 10 μg/cm2. In spatial assays, thyme and cassia were the most active compounds tested with 100% and 80% ticks repelled within 15 min of exposure respectively and was approximately twofold more effective than DEET at the same concentration. To translate these non-host assays to efficacy when used on the human host, we quantified repellency using a finger-climbing assay. TCA, nootkatone and DEET were equally effective in the fingertip assay, and patchouli oil was the only natural oil that significantly repelled ticks. CONCLUSIONS The differences in repellent potency based on the assay type suggests that the ability to discover active tick repellents suitable for development may be more complicated than with other arthropod species; furthermore, the field delivery mechanism must be considered early in development to ensure translation to field efficacy. TCA, which is naturally derived, is a promising candidate for a tick repellent that has comparable repellency to commercialized tick repellents.
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Affiliation(s)
- Anais Le Mauff
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, 2055 Mowry Road, PO Box 100009, Gainesville, FL, 32610, USA
| | - Edmund J Norris
- Center for Medical, Agricultural, and Veterinary Entomology, United States Department of Agriculture, Agricultural Research Service, Gainesville, FL, 32608, USA
| | - Andrew Y Li
- Invasive Insect Biocontrol & Behavior Laboratory, United States Department of Agriculture, Agricultural Research Service, Beltsville, MD, 20705, USA
| | - Daniel R Swale
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, 2055 Mowry Road, PO Box 100009, Gainesville, FL, 32610, USA.
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Swale DR, Bloomquist JR, McComic SE, Burgess ER. Cross resistance to brevetoxin-3 by kdr and super-kdr mutations in house flies. Pestic Biochem Physiol 2024; 201:105898. [PMID: 38685256 DOI: 10.1016/j.pestbp.2024.105898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 03/28/2024] [Accepted: 04/06/2024] [Indexed: 05/02/2024]
Abstract
The dinoflagellate Karenia brevis is a causative agent of red tides in the Gulf of Mexico and generates a potent family of structurally related brevetoxins that act via the voltage-sensitive Na+ channel. This project was undertaken to better understand the neurotoxicology and kdr cross-resistance to brevetoxins in house flies by comparing the susceptible aabys strain to ALkdr (kdr) and JPskdr (super-kdr). When injected directly into the hemocoel, larvae exhibited rigid, non-convulsive paralysis consistent with prolongation of sodium channel currents, the known mechanism of action of brevetoxins. In neurophysiological studies, the firing frequency of susceptible larval house fly central nervous system preparations showed a > 200% increase 10 min after treatment with 1 nM brevetoxin-3. This neuroexcitation is consistent with the spastic paralytic response seen after hemocoel injections. Target site mutations in the voltage-sensitive sodium channel of house flies, known to confer knockdown resistance (kdr and super-kdr) against pyrethroids, attenuated the effect of brevetoxin-3 in baseline firing frequency and toxicity assays. The rank order of sensitivity to brevetoxin-3 in both assays was aabys > ALkdr > JPskdr. At the LD50 level, resistance ratios for the knockdown resistance strains were 6.9 for the double mutant (super-kdr) and 2.3 for the single mutant (kdr). The data suggest that knockdown resistance mutations may be one mechanism by which flies survive brevetoxin-3 exposure during red tide events.
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Affiliation(s)
- Daniel R Swale
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32610, USA.
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32610, USA
| | - Sarah E McComic
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32610, USA
| | - Edwin R Burgess
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32610, USA
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Li Z, McComic S, Chen R, Kim WTH, Gaithuma AK, Mooney B, Macaluso KR, Mulenga A, Swale DR. ATP-sensitive inward rectifier potassium channels regulate secretion of pro-feeding salivary proteins in the lone star tick (Amblyomma americanum). Int J Biol Macromol 2023; 253:126545. [PMID: 37652342 DOI: 10.1016/j.ijbiomac.2023.126545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/22/2023] [Accepted: 08/24/2023] [Indexed: 09/02/2023]
Abstract
Understanding the physiological and molecular regulation of tick feeding is necessary for developing intervention strategies to curb disease transmission by ticks. Pharmacological activation of ATP-gated inward rectifier potassium (KATP) channels reduced fluid secretion from isolated salivary gland and blood feeding in the lone star tick, Amblyomma americanum, yet the temporal expression pattern of KATP channel proteins remained unknown. KATP channels were highly expressed in type II and III acini in off-host stage and early feeding phase ticks, yet expression was reduced in later stages of feeding. We next assessed KATP channel regulation of the secreted proteome of tick saliva. LC-MS/MS analysis identified 40 differentially secreted tick saliva proteins after exposure to KATP activators or inhibitors. Secretion of previously validated tick saliva proteins that promote tick feeding, AV422, AAS27, and AAS41 were significantly reduced by upwards of 8 log units in ticks exposed to KATP channel activators when compared to untreated ticks. Importantly, activation of KATP channels inhibited tick feeding and vice versa for KATP channel inhibitors. Data indicate KATP channels regulate tick feeding biology by controlling secretion of pro-feeding proteins that are essential during early feeding phases, which provides insights into physiological and molecular regulation of tick feeding behavior.
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Affiliation(s)
- Zhilin Li
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, United States of America; Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Sarah McComic
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Rui Chen
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - William Tae Heung Kim
- Department of Veterinary pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA
| | - Alex Kiarie Gaithuma
- Department of Veterinary pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA
| | - Brian Mooney
- Department of Biochemistry, Charles W Gehrlke Proteomics Center, University of Missouri, MO, USA
| | - Kevin R Macaluso
- Department of Microbiology and Immunology, College of Medicine, University of South Alabama, Mobile, AL, USA
| | - Albert Mulenga
- Department of Veterinary pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA
| | - Daniel R Swale
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA.
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Bencosme-Cuevas E, Kim TK, Nguyen TT, Berry J, Li J, Adams LG, Smith LA, Batool SA, Swale DR, Kaufmann SHE, Jones-Hall Y, Mulenga A. Ixodes scapularis nymph saliva protein blocks host inflammation and complement-mediated killing of Lyme disease agent, Borrelia burgdorferi. Front Cell Infect Microbiol 2023; 13:1253670. [PMID: 37965264 PMCID: PMC10641286 DOI: 10.3389/fcimb.2023.1253670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 09/14/2023] [Indexed: 11/16/2023] Open
Abstract
Tick serine protease inhibitors (serpins) play crucial roles in tick feeding and pathogen transmission. We demonstrate that Ixodes scapularis (Ixs) nymph tick saliva serpin (S) 41 (IxsS41), secreted by Borrelia burgdorferi (Bb)-infected ticks at high abundance, is involved in regulating tick evasion of host innate immunity and promoting host colonization by Bb. Recombinant (r) proteins were expressed in Pichia pastoris, and substrate hydrolysis assays were used to determine. Ex vivo (complement and hemostasis function related) and in vivo (paw edema and effect on Bb colonization of C3H/HeN mice organs) assays were conducted to validate function. We demonstrate that rIxsS41 inhibits chymase and cathepsin G, pro-inflammatory proteases that are released by mast cells and neutrophils, the first immune cells at the tick feeding site. Importantly, stoichiometry of inhibition analysis revealed that 2.2 and 2.8 molecules of rIxsS41 are needed to 100% inhibit 1 molecule of chymase and cathepsin G, respectively, suggesting that findings here are likely events at the tick feeding site. Furthermore, chymase-mediated paw edema, induced by the mast cell degranulator, compound 48/80 (C48/80), was blocked by rIxsS41. Likewise, rIxsS41 reduced membrane attack complex (MAC) deposition via the alternative and lectin complement activation pathways and dose-dependently protected Bb from complement killing. Additionally, co-inoculating C3H/HeN mice with Bb together with rIxsS41 or with a mixture (rIxsS41 and C48/80). Findings in this study suggest that IxsS41 markedly contributes to tick feeding and host colonization by Bb. Therefore, we conclude that IxsS41 is a potential candidate for an anti-tick vaccine to prevent transmission of the Lyme disease agent.
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Affiliation(s)
- Emily Bencosme-Cuevas
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Tae Kwon Kim
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, United States
| | - Thu-Thuy Nguyen
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Jacquie Berry
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Jianrong Li
- Department of Veterinary Integrative Biosciences, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Leslie Garry Adams
- Department of Veterinary Physiology and Pharmacology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | | | | | - Daniel R. Swale
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, United States
| | - Stefan H. E. Kaufmann
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
- Hagler Institute for Advanced Study, Texas A&M University, College Station, TX, United States
- Max Planck Institute for Infection Biology, Berlin, Germany
- Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Yava Jones-Hall
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Albert Mulenga
- Department of Veterinary Pathobiology, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
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McComic SE, Duke SO, Burgess ER, Swale DR. Defining the toxicological profile of 4-hydroxyphenylpyruvate dioxygenase-directed herbicides to Aedes aegypti and Amblyomma americanum. Pestic Biochem Physiol 2023; 194:105532. [PMID: 37532340 DOI: 10.1016/j.pestbp.2023.105532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 06/30/2023] [Accepted: 07/11/2023] [Indexed: 08/04/2023]
Abstract
Inhibitors targeting the 4-hydroxyphenyl pyruvate dioxygenase (HPPD) enzyme are well established herbicides and HPPD is also a primary enzyme within the tyrosine metabolism pathway in hematophagous arthropods, which is an essential metaboilic pathway post-blood feeding to prevent tyrosine-mediated toxicity. The objective of this study was to characterize the toxicity of triketone, pyrazole, pyrazolone, isoxazole, and triazole herbicides that inhibit HPPD to blood-fed mosquitoes and ticks. Topical exposure of nitisinone to blood-fed Aedes aegypti yielded high toxicity with an LD50 of 3.81 ng/insect (95% CI: 3.09 to 4.67 ng; Hillslope: 0.97, r2: 0.99), yet was non-toxic to non-blood fed (NBF) mosquitoes. The rank order of toxicity was nitisinone > tembotrione > pyrazoxyfen > tebuconazole > mesotrione against blood-fed Ae. Aegypti, but nitisinone was approximately 30-fold more toxic than other chemicals tested. We also assessed the toxicity of HPPD-inhibiting herbicides to the lone star tick, Amblyomma americanum and similarly, nitisinone was toxic to Am. americanum with a lethal time to kill 50% of subjects (LT50) of 23 h at 10 μM. Knockdown of the gene encoding the HPPD enzyme was performed through RNA-interference led to significant mortality after blood feeding in both, Ae. aegypti and Am. americanum. Lastly, a fluorescence assay was developed to determine relative quantities of L-tyrosine in Ae. aegypti and Am. americanum treated with HPPD inhibitors. L-tyrosine levels correlated with toxicity with nitisinone exposure leading to increased tyrosine concentrations post-blood feeding. Taken together, these data support previous work suggesting HPPD-inhibitors represent a novel mode of toxicity to mosquitoes and ticks and may represent base scaffolds for development of novel insecticides specific for hematophagous arthropods.
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Affiliation(s)
- Sarah E McComic
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA; Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA
| | - Stephen O Duke
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, Oxford, MS 38677, USA
| | - Edwin R Burgess
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Daniel R Swale
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA; Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
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Fellows CJ, Simone-Finstrom M, Anderson TD, Swale DR. Potassium ion channels as a molecular target to reduce virus infection and mortality of honey bee colonies. Virol J 2023; 20:134. [PMID: 37349817 PMCID: PMC10286336 DOI: 10.1186/s12985-023-02104-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 06/16/2023] [Indexed: 06/24/2023] Open
Abstract
Declines in managed honey bee populations are multifactorial but closely associated with reduced virus immunocompetence and thus, mechanisms to enhance immune function are likely to reduce viral infection rates and increase colony viability. However, gaps in knowledge regarding physiological mechanisms or 'druggable' target sites to enhance bee immunocompetence has prevented therapeutics development to reduce virus infection. Our data bridge this knowledge gap by identifying ATP-sensitive inward rectifier potassium (KATP) channels as a pharmacologically tractable target for reducing virus-mediated mortality and viral replication in bees, as well as increasing an aspect of colony-level immunity. Bees infected with Israeli acute paralysis virus and provided KATP channel activators had similar mortality rates as uninfected bees. Furthermore, we show that generation of reactive oxygen species (ROS) and regulation of ROS concentrations through pharmacological activation of KATP channels can stimulate antiviral responses, highlighting a functional framework for physiological regulation of the bee immune system. Next, we tested the influence of pharmacological activation of KATP channels on infection of 6 viruses at the colony level in the field. Data strongly support that KATP channels are a field-relevant target site as colonies treated with pinacidil, a KATP channel activator, had reduced titers of seven bee-relevant viruses by up to 75-fold and reduced them to levels comparable to non-inoculated colonies. Together, these data indicate a functional linkage between KATP channels, ROS, and antiviral defense mechanisms in bees and define a toxicologically relevant pathway that can be used for novel therapeutics development to enhance bee health and colony sustainability in the field.
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Affiliation(s)
- Christopher J Fellows
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, 70803, USA
| | - Michael Simone-Finstrom
- USDA-ARS Honey Bee Breeding, Genetics, and Physiology Laboratory, Baton Rouge, LA, 70820, USA
| | - Troy D Anderson
- Department of Entomology, University of Nebraska, Lincoln, NE, 68583, USA
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, 70803, USA.
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, 2055 Mowry Road, PO Box 100009, Gainesville, FL, 32610, USA.
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Johnson EJ, McComic SE, Rault LC, Swale DR, Anderson TD. Bioinsecticidal activity of cajeput oil to pyrethroid-susceptible and -resistant mosquitoes. Pestic Biochem Physiol 2023; 193:105458. [PMID: 37248001 DOI: 10.1016/j.pestbp.2023.105458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/02/2023] [Accepted: 05/04/2023] [Indexed: 05/31/2023]
Abstract
Mosquito-borne diseases are a significant threat to human health. The frequent and repetitive application of insecticides can result in the selection of resistant mosquito populations leading to product failures for reducing community disease transmission. It is important that new interventions are discovered and developed for reducing mosquito populations and, in turn, protecting human health. Plant essential oils are promising chemical interventions for reducing mosquito populations. The myrtle family, Myrtaceae, has numerous species to be studied as potential bioinsecticides. Here, we combined toxicological, biochemical, and neurophysiological approaches to provide evidence for cajeput oil and terpene constituents to elicit bioinsecticidal activity to pyrethroid-susceptible and -resistant Aedes aegypti. We show cajeput oil terpenes to enhance cAMP production, increase ACh levels, inhibit in vivo and in vitro AChE activity, and disrupt spike discharge frequencies of the mosquito CNS. This study presents the first report on the bioinsecticidal activity of cajeput oil terpenes to pyrethroid-susceptible and -resistant mosquitoes and provides comparative data for the octopaminergic system as a putative molecular target for the bioinsecticides with implications for resistance management.
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Affiliation(s)
- Ellis J Johnson
- Department of Entomology, University of Nebraska, 103 Entomology Hall, 1700 East Campus Mall, Lincoln, NE 68583, USA
| | - Sarah E McComic
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, 2055 Mowry Road, PO Box 100009, Gainesville, FL 32610, USA
| | - Leslie C Rault
- Department of Entomology, University of Nebraska, 103 Entomology Hall, 1700 East Campus Mall, Lincoln, NE 68583, USA
| | - Daniel R Swale
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, 2055 Mowry Road, PO Box 100009, Gainesville, FL 32610, USA
| | - Troy D Anderson
- Department of Entomology, University of Nebraska, 103 Entomology Hall, 1700 East Campus Mall, Lincoln, NE 68583, USA.
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Chen R, Swale DR. Functional interactions between potassium-chloride cotransporter (KCC) and inward rectifier potassium (Kir) channels in the insect central nervous system. Pestic Biochem Physiol 2023; 192:105389. [PMID: 37105628 DOI: 10.1016/j.pestbp.2023.105389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 03/07/2023] [Accepted: 03/07/2023] [Indexed: 06/19/2023]
Abstract
The K+/Cl- cotransporter (KCC) is the primary mechanism by which mature neurons maintain low intracellular chloride (Cl-) concentration and has been shown to be functionally coupled to the GABA-gated chloride channels (GGCC) in Drosophila central neurons. Further, pharmacological inhibition of KCC has been shown to lead to acute toxicity of mosquitoes that highlights the toxicological relevance of insect KCC. Yet, gaps in knowledge remain regarding physiological drivers of KCC function and interactions of ion flux mechanisms upstream of GGCC in insects. Considering this, we employed electrophysiological and fluorescent microscopy techniques to further characterize KCC in the insect nervous system. Fluorescent microscopy indicated insect KCC2 is expressed in rdl neurons, which is the neuron type responsible for GABA-mediated neurotransmission, and are coexpressed with inward rectifier potassium (Kir) 2 channels. Coexpression of Kir2 and KCC2 suggested the possibility of functional coupling between these two K+ flux pathways. Indeed, extracellular recordings of Drosophila CNS showed pre-block of Kir channels prior to block of KCC led to a significant (P < 0.001) increase in CNS firing rates over baseline that when taken together, supports functional coupling of Kir to KCC function. Additionally, we documented a synergistic increase to toxicity of VU0463271, an established KCC inhibitor, above the expected additive toxicity after co-treatment with the Kir inhibitor, VU041. These data expand current knowledge regarding the physiological roles of KCC and Kir channels in the insect nervous system by defining additional pathways that facilitate inhibitory neurotransmission through GGCC.
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Affiliation(s)
- Rui Chen
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, United States of America
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, United States of America; Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, United States of America.
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Duke SO, Pan Z, Chittiboyina AG, Swale DR, Sparks TC. Molecular targets of insecticides and herbicides - Are there useful overlaps? Pestic Biochem Physiol 2023; 191:105340. [PMID: 36963955 DOI: 10.1016/j.pestbp.2023.105340] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 01/07/2023] [Accepted: 01/10/2023] [Indexed: 06/18/2023]
Abstract
New insecticide modes of action are needed for insecticide resistance management strategies. The number of molecular targets of commercial herbicides and insecticides are fewer than 35 for both. Few commercial insecticide targets are found in plants, but ten targets of commercial herbicides are found in insects. For several of these commonly held targets, some compounds kill both plants and insects. For example, herbicidal inhibitors of p-hydroxyphenylpyruvate dioxygenase are effective insecticides on blood-fed insects. The glutamine synthetase-inhibiting herbicide glufosinate is insecticidal by the same mechanism of action, inhibition of glutamine synthetase. These and other examples of shared activities of commercial herbicides with insecticides through the same target site are discussed. Compounds with novel herbicide targets shared by insects that are not commercialized as pesticides (such as statins) are also discussed. Compounds that are both herbicidal and insecticidal can be used for insect pests not associated with crops or with crops made resistant to the compounds.
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Affiliation(s)
- Stephen O Duke
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38667, USA.
| | - Zhiqiang Pan
- Natural Products Utilization Research Unit, United States Department of Agriculture, University, MS 38667, USA
| | - Amar G Chittiboyina
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38667, USA
| | - Daniel R Swale
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA
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O'Hara FM, Liu Z, Davis JA, Swale DR. Catalyzing systemic movement of inward rectifier potassium channel inhibitors for antifeedant activity against the cotton aphid, Aphis gossypii (Glover). Pest Manag Sci 2023; 79:194-205. [PMID: 36116013 DOI: 10.1002/ps.7188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/26/2022] [Accepted: 09/18/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a destructive agricultural pest, capable of photosynthate removal and plant virus transmission. Therefore, we aimed to test the antifeedant properties of small-molecule inhibitors of inward rectifier potassium (Kir) channels expressed in insect salivary glands and develop an approach for enabling systemic movement of lipophilic Kir inhibitors. RESULTS Two Kir channel inhibitors, VU041 and VU730, reduced the secretory activity of the aphid salivary glands by 3.3-fold and foliar applications of VU041 and VU730 significantly (P < 0.05) increased the time to first probe, total probe duration, and nearly eliminated phloem salivation and ingestion. Next, we aimed to facilitate systemic movement of VU041 and VU730 through evaluation of a novel natural product based solubilizer containing rubusoside that was isolated from Chinese sweet leaf (Rubus suavissimus) plants. A single lower leaf was treated with Kir inhibitor soluble liquid (KI-SL) and systemic movement throughout the plant was verified via toxicity bioassays and changes to feeding behavior through the electrical penetration graph (EPG) technique. EPG data indicate KI-SL significantly reduced ability to reach E1 (phloem salivation) and E2 (phloem ingestion) waveforms and altered plant probing behavior when compared to the untreated control. High-performance liquid chromatography (HPLC) analysis indicated the presence of VU041 and VU730 in the upper leaf tissue of these plants. Together, these data provide strong support that incorporation of rubusoside with Kir inhibitors enhanced translaminar and translocation movement through the plant tissue. CONCLUSION These data further support hemipteran Kir channels as a target to prevent feeding and induce toxicity. Further, these studies highlight a novel delivery approach for generating plant systemic activity of lipophilic insecticides. © 2022 Society of Chemical Industry.
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Affiliation(s)
- Flinn M O'Hara
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Zhijun Liu
- School of Renewable Natural Resources, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Jeffrey A Davis
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
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Fellows CJ, Anderson TD, Swale DR. Acute toxicity of atrazine, alachlor, and chlorpyrifos mixtures to honey bees. Pestic Biochem Physiol 2022; 188:105271. [PMID: 36464376 DOI: 10.1016/j.pestbp.2022.105271] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/19/2022] [Accepted: 10/19/2022] [Indexed: 06/17/2023]
Abstract
The acute toxicity of chlorpyrifos and chlorpyrifos-oxon (organophosphorothioate insecticides) was examined alone and in combination with atrazine (triazine herbicide) and alachlor (chloroacetanilide herbicide) to honey bees (Apis mellifera). Atrazine and alachlor were observed to not be acutely toxic to bees at doses up to 10 and 4 μg per bee, respectively. However, atrazine significantly increased chlorpyrifos toxicity by 3-fold while reducing chlorpyrifos-oxon toxicity by 1.8-fold. These changes in toxicity are correlated with significant 1.3- and 1.2-fold inhibition of acetylcholinesterase (AChE) activity in bees exposed to chlorpyrifos and chlorpyrifos-oxon, respectively. Atrazine significantly increased cytochrome P450, general esterase, and glutathione S-transferase (GST) activities by 1.5-, 1.2-, and 1.2- fold respectively, in bees compared to untreated individuals. Alachlor increased chlorpyrifos toxicity by 2.5-fold but did not affect the toxicity of chlorpyrifos-oxon. Exposure to alachlor and chlorpyrifos did not affect AChE compared to chlorpyrifos alone. However, exposure to chlorpyrifos-oxon and alachlor significantly increased acetylcholinesterase (AChE) activity by 1.4-fold. GST activity, but not P450 or general esterases, was significantly increased in bees exposed to alachlor. These data provide evidence that triazine and chloroacetanilide herbicide exposure alters detoxification enzyme activity and, in turn, alters the sensitivity of bees to organophosphorothioate insecticides. Importantly, these data can be used to guide future studies aiming to test safety profiles for pollinators and expand regulatory framework required for pesticide registration.
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Affiliation(s)
| | - Troy D Anderson
- Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA; Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32610, USA.
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O'Hara FM, Davis JA, Swale DR. Profile of commercialized aphicides on the survivorship and feeding behavior of the cotton aphid, Aphis gossypii. Pestic Biochem Physiol 2022; 186:105174. [PMID: 35973765 DOI: 10.1016/j.pestbp.2022.105174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 07/05/2022] [Accepted: 07/07/2022] [Indexed: 06/15/2023]
Abstract
The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most destructive agricultural pests due to photosynthate removal and horizontal transmission of plant viruses. Horizontal transmission of plant viruses by aphids occurs during distinct feeding behavioral events, such as probing for non-persistent viruses or phloem feeding for persistent viruses. We employed toxicity bioassays and electrical penetration graph (EPG) methodology to compare toxicity and quantify changes to feeding behavior and toxicity of A. gossypii after exposure to commercialized aphicides. Commercialized aphicides containing flupyradifurone, sulfoxaflor, thiamethoxam, thiamethoxam + lambda cyhalothrin, and bifenthrin induced >90% aphid mortality within 4 h of exposure. Flupyradifurone was the most acutely toxic aphicide studied with an LT50 of 8.9 min after exposure, which was approximately 3-fold lower than bifenthrin and thiamethoxam + lambda cyhalothrin. This was supported by our EPG results that showed a significant reduction in the proportion of aphids that continued to probe on cotton 4 h after exposure to flonicamid, thiamethoxam, flupyradifurone, bifenthrin, and thiamethoxam + lambda cyhalothrin. The commercialized aphicides containing spirotetramat, flonicamid, thiamethoxam, flupyradifurone, bifenthrin, sulfoxaflor, and pymetrozine significantly (P < 0.05) decreased the time to first probe when compared to the untreated control. Lastly, E1 (phloem salivation) and E2 (phloem ingestion) waveforms were significantly (P < 0.05) reduced for flupyradifurone, flonicamid, thiamethoxam, sulfoxaflor, and thiamethoxam. These data provide a comparative study for the development of new aphicides aiming to induce acute lethality and reduce aphid transmission of plant viruses.
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Affiliation(s)
- Flinn M O'Hara
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA 70803, United States of America
| | - Jeffrey A Davis
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA 70803, United States of America
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA 70803, United States of America.
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13
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Norris EJ, Chen R, Li Z, Geldenhuys W, Bloomquist JR, Swale DR. Mode of action and toxicological effects of the sesquiterpenoid, nootkatone, in insects. Pestic Biochem Physiol 2022; 183:105085. [PMID: 35430075 DOI: 10.1016/j.pestbp.2022.105085] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/16/2022] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Nootkatone, a sesquiterpenoid isolated from Alaskan yellow cedar (Cupressus nootkatensis), is known to possess insect repellent and acaricidal properties and has recently been registered for commercial use by the Environmental Protection Agency. Previous studies failed to elucidate the mechanism of action of nootkatone, but we found a molecular overlay of picrotoxinin and nootkatone indicated a high degree of structural and electrostatic similarity. We therefore tested the hypothesis that nootkatone was a GABA-gated chloride channel antagonist, similar to picrotoxinin. The KD50 and LD50 of nootkatone on the insecticide-susceptible strain of Drosophila melanogaster (CSOR) showed resistance ratios of 8 and 11, respectively, compared to the cyclodiene-resistant strain of RDL1675, indicating significant cross-resistance. Nootkatone reversed GABA-mediated block of the larval CSOR central nervous system; nerve firing of 78 ± 17% of baseline in the CSOR strain was significantly different from 24 ± 11% of baseline firing in the RDL1675 strain (p = 0.035). This finding indicated that the resistance was expressed within the nervous system. Patch clamp recordings on D. melanogaster central neurons mirrored extracellular recordings where nootkatone inhibited GABA-stimulated currents by 44 ± 9% at 100 μM, whereas chloride current was inhibited 4.5-fold less at 100 μM in RDL1675. Taken together, these data suggest nootkatone toxicity in D. melanogaster is mediated through GABA receptor antagonism.
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Affiliation(s)
- Edmund J Norris
- Emerging Pathogens Institute, Entomology and Nematology Department, 2055 Mowry Road, University of Florida, Gainesville, FL 32610-0009, USA; USDA/ARS Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32610-0009, USA
| | - Rui Chen
- Louisiana State University Agricultural Center, Department of Entomology, Baton Rouge, LA 70803, USA
| | - Zhilin Li
- Louisiana State University Agricultural Center, Department of Entomology, Baton Rouge, LA 70803, USA
| | - Werner Geldenhuys
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Entomology and Nematology Department, 2055 Mowry Road, University of Florida, Gainesville, FL 32610-0009, USA
| | - Daniel R Swale
- Louisiana State University Agricultural Center, Department of Entomology, Baton Rouge, LA 70803, USA.
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Li Z, Soohoo-Hui A, O’Hara FM, Swale DR. ATP-sensitive inward rectifier potassium channels reveal functional linkage between salivary gland function and blood feeding in the mosquito, Aedes aegypti. Commun Biol 2022; 5:278. [PMID: 35347209 PMCID: PMC8960802 DOI: 10.1038/s42003-022-03222-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 03/02/2022] [Indexed: 12/03/2022] Open
Abstract
Reducing saliva secretions into the vertebrate host reduces feeding efficacy by most hematophagous arthropods. However, seminal studies suggested saliva is not a prerequisite for blood feeding in Aedes aegypti. To test this paradigm, we manually transected the salivary duct of female A. aegypti and an inability to salivate was correlated to an inability to imbibe blood. These data justified testing the relevance of inwardly rectifying potassium (Kir) channels in the A. aegypti salivary gland as an antifeedant target site. Pharmacological activation of ATP-gated Kir (KATP) channels reduced the secretory activity of the salivary gland by 15-fold that led to near elimination of blood ingestion during feeding. The reduced salivation and feeding success nearly eliminated horizontal transmission and acquisition of Dengue virus-2 (DENV2). These data suggest mosquito salivation is a prerequisite for blood feeding and provide evidence that KATP channels are critical for salivation, feeding, and vector competency. The salivary gland of Aedes aegypti is needed for efficient blood feeding, and disruption of ATP-gated Kir channels prevents salivation and blood feeding in A. aegypti as well as horizontal transmission and acquisition of Dengue virus2.
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Abstract
Inward rectifier K+ (Kir) channels have been studied extensively in mammals, where they play critical roles in health and disease. In insects, Kir channels have recently been found to be key regulators of diverse physiological processes in several tissues. The importance of Kir channels in insects has positioned them to serve as emerging targets for the development of insecticides with novel modes of action. In this article, we provide the first comprehensive review of insect Kir channels, highlighting the rapid progress made in understanding their molecular biology, physiological roles, pharmacology, and toxicology. In addition, we highlight key gaps in our knowledge and suggest directions for future research to advance our understanding of Kir channels and their roles in insect physiology. Further knowledge of their functional roles will also facilitate their exploitation as targets for controlling arthropod pests and vectors of economic, medical, and/or veterinary relevance.
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Affiliation(s)
- Peter M Piermarini
- Department of Entomology, The Ohio State University, Wooster, Ohio 44691, USA;
| | - Jerod S Denton
- Departments of Anesthesiology & Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37235, USA;
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, Louisiana 70803, USA;
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McComic SE, Meepagala KM, Swale DR. Characterization of Toxicological and Neurophysiological Effects of Natural Product Based Chromenes to Fall Armyworm, Spodoptera frugiperda. J Econ Entomol 2021; 114:2485-2492. [PMID: 34499738 DOI: 10.1093/jee/toab172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Indexed: 06/13/2023]
Abstract
We previously extracted and purified a chromene amide from Amyris texana and found this scaffold is moderately insecticidal and thus, this study aimed to test the insecticidal properties of 13 synthetically derived chromene analogs to the fall armyworm (FAW, Spodoptera frugiperda). Microinjection of chromenes with alcohol or aldehydes substitutions at the meta position on the benzopyran moiety led to moderate toxicity that was approximately 2- to 3-fold less toxic when compared to permethrin, yet microinjection of differently substituted chromenes exhibited little to no toxicity. Similarly, chromenes with alcohol or aldehydes substitutions at the meta position on the benzopyran moiety were among the most toxic chromenes studied through ingested exposure. In addition to acute toxicity, select chromenes significantly increased the percentage of developmental defects upon eclosion that prevented adult moths from being capable of flight, suggesting these compounds alter development. Interestingly, microinjection yielded differing signs of intoxication between alcohol and aldehyde substitutions where the alcohol resulted in flaccid paralysis and lethargy whereas aldehyde led to tonic contractions and hyperactivity. These contrasting signs of intoxication were also observed in electrophysiological assays where alcohol substitutions led to the depression of central neuron firing activity and aldehyde substitutions led to hyperexcitation of central neurons. In summary, the chromene amides led to acute lethality and/or altered developmental trajectories of FAW, yet the high doses required for acute mortality suggest these scaffolds hold relatively little promise for development into FAW-directed insecticides but may represent novel growth regulators for FAW.
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Affiliation(s)
- Sarah E McComic
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA 70803, USA
| | - Kumudini M Meepagala
- Natural Products Utilization Research Unit, USDA-ARS, PO Box 1848, University, MS 38677, USA
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA 70803, USA
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17
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McComic SE, Rault LC, Anderson TD, Swale DR. Toxicological analysis of stilbenes against the fall armyworm, Spodoptera frugiperda. Pestic Biochem Physiol 2021; 179:104965. [PMID: 34802515 DOI: 10.1016/j.pestbp.2021.104965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 08/17/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
The fall armyworm (FAW), Spodoptera frugiperda, is a global pest of multiple economically important row crops and the development of resistance to commercially available insecticidal classes has inhibited FAW control. Thus, there is a need to identify chemical scaffolds that can provide inspiration for the development of novel insecticides for FAW management. This study aimed to assess the sensitivity of central neurons and susceptibility of FAW to chloride channel modulators to establish a platform for repurposing existing insecticides or designing new chemicals capable of controlling FAW. Potency of select chloride channel modulators were initially studied against FAW central neuron firing rate and rank order of potency was determined to be fipronil > lindane > Z-stilbene > DIDS > GABA > E-stilbene. Toxicity bioassays identified fipronil and lindane as the two most toxic modulators studied with topical LD50's of 41 and 75 ng/mg of caterpillar, respectively. Interestingly, Z-stilbene was toxic at 300 ng/mg of caterpillar, but no toxicity was observed with DIDS or E-stilbene. The significant shift in potency between stilbene isomers indicates structure-activity relationships between stilbene chemistry and the binding site in FAW may exist. The data presented in this study defines the potency of select chloride channel modulators to FAW neural activity and survivorship to establish a platform for development of novel chemical agents to control FAW populations. Although stilbenes may hold promise for insecticide development, the low toxicity of the scaffolds tested in this study dampen enthusiasm for their development into FAW specific insecticides.
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Affiliation(s)
- Sarah E McComic
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States of America
| | - Leslie C Rault
- University of Nebraska, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583, United States of America
| | - Troy D Anderson
- University of Nebraska, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583, United States of America
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States of America.
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18
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Soohoo-Hui A, Li Z, Maldonado-Ruiz LP, Zhang G, Swale DR. Neurochemical regulation of Aedes aegypti salivary gland function. J Insect Physiol 2021; 129:104193. [PMID: 33460707 DOI: 10.1016/j.jinsphys.2021.104193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 12/15/2020] [Accepted: 01/11/2021] [Indexed: 06/12/2023]
Abstract
The salivary gland of hematophagous arthropods is critical for blood meal acquisition, blood vessel localization, and secretion of digestive enzymes. Thus, there is significant interest in the regulation of salivary gland function and mechanisms driving the secretion of saliva and digestive proteins. We aimed to gain a broader understanding of the regulatory role of aminergic, cholinergic, and octopaminergic neuromodulators to saliva and protein secretion from the female A. aegypti salivary gland. Quantification of saliva after injection with neuromodulators showed that dopamine, serotonin, and pilocarpine increased the secretory activity of the salivary gland with potency rankings dopamine = serotonin > pilocarpine. No change in saliva secretion was observed with octopamine or ergonovine, which indicates the A. aegypti salivary gland may be regulated by dopaminergic, serotonergic, and cholinergic systems, but are not likely regulated by octopaminergic or tryptaminergic systems. Next, we studied the regulatory control of dopamine-mediated salivation. Data indicate extracellular calcium flux, but not neural function, is critical for dopamine-mediated salivation, which suggests epithelial transport of ions and not neuronal control is responsible for dopamine-mediated salivation. For regulation of protein secretion, data indicate dopamine or serotonin exposure facilitates amylase secretion, whereas serotonin but not dopamine exposure increased apyrase concentrations in the secreted saliva. General immunoreactivity to anti-rat D1-dopamine receptor antibody was observed, yet immunoreactivity to the anti-rat D2-receptor antibody was identified in the proximal regions of the lateral lobes and slight immunoreactivity in the distal portion of the lateral lobe, with no expression in the medial lobe.
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Affiliation(s)
- Alexander Soohoo-Hui
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, USA
| | - Zhilin Li
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, USA
| | | | - Ganyu Zhang
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, USA; Beijing Key Laboratory for Forest Pest Control, Beijing Forestry University, Beijing 100083, China
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, USA.
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19
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McComic SE, Rault LC, Anderson TD, Swale DR. Reduced neuronal sensitivity and susceptibility of the fall armyworm, Spodoptera frugiperda, to pyrethroids in the absence of known knockdown mutations. Pestic Biochem Physiol 2020; 169:104652. [PMID: 32828370 DOI: 10.1016/j.pestbp.2020.104652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 07/06/2020] [Accepted: 07/09/2020] [Indexed: 06/11/2023]
Abstract
Neurophysiological recordings were employed to quantify neuronal sensitivity to neurotoxic insecticides and assessed toxicity across field and laboratory fall armyworm (FAW) populations. Topical toxicity resistance ratios (RR) in field-collected FAW was 767-fold compared to laboratory strains and, importantly, a 1750-fold reduction in potency was observed for λ-cyhalothrin in neurophysiological assays. Field collected FAW were found to have a RR of 12 to chlorpyrifos when compared to the susceptible strain and was 8-fold less sensitive in neurophysiological assays. Surprisingly, there were no point mutations identified in the voltage-gated sodium channel known to cause pyrethroid resistance. For acetylcholinesterase, FAW had more than 80% of their nucleotide sequences consistent with A201 and F290 of the susceptible strains although 60% of the tested population was heterozygous for the G227A mutation. These data indicate that point mutations did not contribute to the high level of pyrethroid resistance and nerve insensitivity in this population of field collected FAW. Additionally, these data suggest the kdr phenotype only explains a portion of the heritable variation in FAW resistance and indicates kdr is not the only predictor of high pyrethroid resistance. Phenotypic assays, such as toxicity bioassays or neurophysiological recordings, using field-collected populations are necessary to reliably predict resistant phenotypes and product failures.
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Affiliation(s)
- Sarah E McComic
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States of America
| | - Leslie C Rault
- University of Nebraska, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583, United States of America
| | - Troy D Anderson
- University of Nebraska, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583, United States of America
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States of America.
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20
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Williams JR, Swale DR, Anderson TD. Comparative effects of technical-grade and formulated chlorantraniliprole to the survivorship and locomotor activity of the honey bee, Apis mellifera (L.). Pest Manag Sci 2020; 76:2582-2588. [PMID: 32237052 DOI: 10.1002/ps.5832] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/27/2020] [Accepted: 04/01/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND The loss of honey bee colonies is a nationally recognized problem that demands attention from both the scientific community and the beekeeping industry. One outstanding threat is the unintended exposure of these pollinators to agricultural pesticides. Anthranilic diamides, such as chlorantraniliprole, are registered for use in stone and pome fruits, vegetables, turf, and grains. There are few publicly available studies that provide an analysis of chlorantraniliprole effects on the survivorship and locomotion activity of beneficial, pollinating insects such as honey bees. The data gathered in this study provide the acute toxicity, 30-day survivorship, and locomotor activity of honey bees exposed to technical-grade chlorantraniliprole and three formulated products with chlorantraniliprole as the active ingredient. RESULTS Neither the technical-grade nor the formulated products of chlorantraniliprole were acutely toxic to honey bees following 4 or 72h treatments at the tested concentrations. A 4 h treatment of technical-grade and formulated chlorantraniliprole did not significantly affect the 30-day survivorship, although significantly higher mortality was observed after 30 days for bees receiving a 72 h treatment of technical-grade chlorantraniliprole and two formulated products. The locomotion activity, or total walking distance, of bees receiving a 4 h treatment of one chlorantraniliprole formulation was significantly reduced, with these individuals recovering their normal locomotion activity at 48 h post exposure. Conversely, there was observed lethargic behavior and significantly reduced walking distances for bees provided with a 72 h treatment of technical-grade chlorantraniliprole and each formulated product. CONCLUSION This study provides evidence for the effect of long-term exposure of chlorantraniliprole on the survivorship and locomotor activity of honey bees. Bees receiving a more field-relevant short-term exposure survived and moved similarly to untreated bees, reiterating the relative safety of chlorantraniliprole exposure to adult honey bees at recommended label concentrations. © 2020 Society of Chemical Industry.
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Affiliation(s)
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, Louisiana, USA
| | - Troy D Anderson
- Department of Entomology, University of Nebraska, Lincoln, NE, USA
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21
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Li Z, Guerrero F, Pérez de León AA, Foil LD, Swale DR. Small-Molecule Inhibitors of Inward Rectifier Potassium (Kir) Channels Reduce Bloodmeal Feeding and Have Insecticidal Activity Against the Horn Fly (Diptera: Muscidae). J Med Entomol 2020; 57:1131-1140. [PMID: 32006426 DOI: 10.1093/jme/tjaa015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Indexed: 06/10/2023]
Abstract
Bloodmeal feeding by the horn fly, Haematobia irritans (L.), is associated with reduced milk production and blood loss that ultimately prevents weight gain of calves and yearlings. Thus, blood feeding by H. irritans causes significant economic losses in several continents. As with other arthropods, resistance to the majority of commercialized insecticides reduces the efficacy of current control programs. Thus, innovative technologies and novel biochemical targets for horn fly control are needed. Salivary gland and Malpighian tubule function are critical for H. irritans survivorship as they drive bloodmeal acquisition and maintain ion- and fluid homeostasis during bloodmeal processing, respectively. Experiments were conducted to test the hypothesis that pharmacological modulation of H. irritans inward rectifier potassium (Kir) channels would preclude blood feeding and induce mortality by reducing the secretory activity of the salivary gland while simultaneously inducing Malpighian tubule failure. Experimental results clearly indicate structurally diverse Kir channel modulators reduce the secretory activity of the salivary gland by up to fivefold when compared to control and the reduced saliva secretion was highly correlated to a reduction in bloodmeal acquisition in adult flies. Furthermore, adult feeding on blood treated with Kir channel modulators resulted in significant mortality. In addition to validating the Kir channels of H. irritans as putative insecticide targets, the knowledge gained from this study could be applied to develop novel therapeutic technologies targeting salivary gland or Malpighian tubule function to reduce the economic burden of horn fly ectoparasitism on cattle health and production.
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Affiliation(s)
- Zhilin Li
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA
| | | | - Adalberto A Pérez de León
- Knipling-Bushland Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service, Kerrville, TX
| | - Lane D Foil
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA
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Swale DR. Perspectives on new strategies for the identification and development of insecticide targets. Pestic Biochem Physiol 2019; 161:23-32. [PMID: 31685193 DOI: 10.1016/j.pestbp.2019.07.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/02/2019] [Accepted: 07/02/2019] [Indexed: 06/10/2023]
Abstract
The discovery and development of new active ingredients to control arthropod populations and circumvent the inevitable evolution of insecticide resistance has been of consistent interest to the field of insecticide science. This interest has resulted in a slow, but steady increase in the diversity of chemical scaffolds and biochemical target sites within the insecticide arsenal over the past 70 years with growth from three biochemical target sites in the 1950s to 22 distinct biochemical targets in 2018. Despite this growth, the number of biochemical target sites for insecticides remains relatively limited when compared to human pharmaceuticals, which has approximately 700 distinct biochemical targets that are targeted by FDA approved drugs. Potential reasons for this large discrepancy between two closely related fields and putative mechanisms to enhance the identification of tractable biochemical targets for insecticides are discussed. Next, this perspective discusses the movement of insecticide science into the "genomic era" and for comparative purposes, I provide a retrospective analysis of the impact the release of the human genome had to human pharmaceutical development. Based on this analysis and because the fields of insecticide science and human pharmaceuticals mirror each other, researchers in the field of insecticide science would do well to heed the lessons learned by the human pharmaceutical industry and to carefully consider the challenges that arise from genomic approaches for chemical development. Lastly, I pose the question if the field of insecticide science would benefit from adapting an industry-academia model through the generation of industry-sponsored centers of excellence. The goal of this article is not to definitively describe strategies to enhance insecticide development, but rather present different thoughts on agrochemical development that will foster discussions among academic, government, and industry scientists to address current and future problems in the field of insecticide science.
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Affiliation(s)
- Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA 70803, United States of America.
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23
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Li Z, Davis JA, Swale DR. Chemical inhibition of Kir channels reduces salivary secretions and phloem feeding of the cotton aphid, Aphis gossypii (Glover). Pest Manag Sci 2019; 75:2725-2734. [PMID: 30785236 DOI: 10.1002/ps.5382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/12/2019] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND The unique feeding biology of aphids suggests novel insecticide targets are likely to exist outside of the nervous system. We therefore aimed to directly test the hypothesis that pharmacological inhibition of inward rectifier potassium (Kir) channels would result in salivary gland failure and reduced sap ingestion by the cotton aphid, Aphis gossypii. RESULTS The Kir inhibitors VU041 and VU590 reduced the length of the salivary sheath in a concentration dependent manner, indicating that the secretory activity of the salivary gland is reduced by Kir inhibition. Next, we employed the electrical penetration graph (EPG) technique to measure the impact Kir inhibition has to aphid sap feeding and feeding biology. Data show that foliar application of VU041 eliminated the E1 and E2 phases (phloem feeding) in all aphids studied. Contact exposure to VU041 after foliar applications was found to be toxic to A. gossypii at 72 and 96 h post-infestation, indicating mortality is likely a result of starvation and not acute toxicity. Furthermore, VU041 exposure significantly altered the feeding behavior of aphids, which is toxicologically relevant for plant-virus interactions. CONCLUSION These data suggest Kir channels are critical for proper function of aphid salivary glands and the reduced plant feeding justifies future work in developing salivary gland Kir channels as novel mechanism aphicides. Furthermore, products like VU041 would add to a very minor arsenal of compounds that simultaneously reduce vector abundance and alter feeding behavior. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Zhilin Li
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Jeffrey A Davis
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
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Swale DR, Bloomquist JR. Is DEET a dangerous neurotoxicant? Pest Manag Sci 2019; 75:2068-2070. [PMID: 31069958 DOI: 10.1002/ps.5476] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 06/09/2023]
Abstract
Controversies surrounding the safety of N,N-diethyl-meta-toluamide (DEET) when used as an insect repellent are centered around conflicting findings in the scientific literature and inaccurate reporting in the public media. Lethal cases of DEET poisoning are few, and usually due to deliberate or other overdoses that ignore product label instructions. Deleterious effects of DEET typically involve skin reactions and even when encephalopathies, such as seizures, occur they often abate without sequelae. Recent mode-of-action studies prove it has little direct effect on acetylcholinesterase, and have identified G protein-coupled receptors as a site of action deserving of further investigation. Studies with pregnant women found that DEET had no effect on the developing fetus from proper use and its continued deployment as a repellent is endorsed by both the Centers for Disease Control and Prevention and the Environmental Protection Agency, with specific recommendations of how it should be used on children. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Jeffrey R Bloomquist
- Neurotoxicology Laboratory, Entomology and Nematology Department, Emerging Pathogens Institute, Gainesville, FL, USA
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Chen R, Prael FJ, Li Z, Delpire E, Weaver CD, Swale DR. Functional Coupling of K +-Cl - Cotransporter (KCC) to GABA-Gated Cl - Channels in the Central Nervous System of Drosophila melanogaster Leads to Altered Drug Sensitivities. ACS Chem Neurosci 2019; 10:2765-2776. [PMID: 30942574 DOI: 10.1021/acschemneuro.8b00697] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
GABAergic signaling is the cornerstone for fast synaptic inhibition of neural signaling in arthropods and mammals and is the molecular target for insecticides and pharmaceuticals, respectively. The K+-Cl- cotransporter (KCC) is the primary mechanism by which mature neurons maintain low intracellular Cl- concentration, yet the fundamental physiology, comparative physiology, and toxicological relevance of insect KCC is understudied. Considering this, we employed electrophysiological, genetic, and pharmacological methods to characterize the physiological underpinnings of KCC function to the Drosophila CNS. Our data show that genetic ablation or pharmacological inhibition of KCC results in an increased spike discharge frequency and significantly ( P < 0.05) reduces the CNS sensitivity to γ-aminobutyric acid (GABA). Further, simultaneous inhibition of KCC and ligand-gated chloride channel (LGCC) complex results in a significant ( P < 0.001) increase in CNS spontaneous activity over baseline firing rates that supports functional coupling of KCC to LGCC function. Interestingly, 75% reduction in KCC mRNA did not alter basal neurotransmission levels indicating that only a fraction of the KCC population is required to maintain the Cl- ionic gradient when at rest, but prolonged synaptic activity increases the threshold for GABA-mediated inhibition and reduces nerve sensitivity to GABA. These data expand current knowledge regarding the physiological role of KCC in a model insect and provides the necessary foundation to develop KCC as a novel biochemical target of insecticides, as well as complements existing research to provide a holistic understanding of the plasticity in mammalian health and disease.
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Affiliation(s)
- Rui Chen
- Department of Entomology , Louisiana State University AgCenter , Baton Rouge , Louisiana 70803 , United States
| | - Francis J Prael
- Department of Pharmacology , Vanderbilt University , Nashville , Tennessee 37232 , United States
- Vanderbilt Institute of Chemical Biology , Vanderbilt University , Nashville , Tennessee 37232 , United States
| | - Zhilin Li
- Department of Entomology , Louisiana State University AgCenter , Baton Rouge , Louisiana 70803 , United States
| | - Eric Delpire
- Department of Anesthesiology , Vanderbilt University School of Medicine , Nashville , Tennessee 37232 , United States
| | - C David Weaver
- Department of Pharmacology , Vanderbilt University , Nashville , Tennessee 37232 , United States
- Vanderbilt Institute of Chemical Biology , Vanderbilt University , Nashville , Tennessee 37232 , United States
| | - Daniel R Swale
- Department of Entomology , Louisiana State University AgCenter , Baton Rouge , Louisiana 70803 , United States
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Swale DR, Gross AD, Coquerel QRR, Bloomquist JR. Electrophysiological Recording of The Central Nervous System Activity of Third-Instar Drosophila Melanogaster. J Vis Exp 2018. [PMID: 30531714 DOI: 10.3791/58375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The majority of the currently available insecticides target the nervous system and genetic mutations of invertebrate neural proteins oftentimes yield deleterious consequences, yet the current methods for recording nervous system activity of an individual animal is costly and laborious. This suction electrode preparation of the third-instar larval central nervous system of Drosophila melanogaster, is a tractable system for testing the physiological effects of neuroactive agents, determining the physiological role of various neural pathways to CNS activity, as well as the influence of genetic mutations to neural function. This ex vivo preparation requires only moderate dissecting skill and electrophysiological expertise to generate reproducible recordings of insect neuronal activity. A wide variety of chemical modulators, including peptides, can then be applied directly to the nervous system in solution with the physiological saline to measure the influence on the CNS activity. Further, genetic technologies, such as the GAL4/UAS system, can be applied independently or in tandem with pharmacological agents to determine the role of specific ion channels, transporters, or receptors to arthropod CNS function. In this context, the assays described herein are of significant interest to insecticide toxicologists, insect physiologists, and developmental biologists for which D. melanogaster is an established model organism. The goal of this protocol is to describe an electrophysiological method to enable the measurement of electrogenesis of the central nervous system in the model insect, Drosophila melanogaster, which is useful for testing a diversity of scientific hypotheses.
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Affiliation(s)
- Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter;
| | | | - Quentin R R Coquerel
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida
| | - Jeffrey R Bloomquist
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida
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Prael FJ, Chen R, Li Z, Reed CW, Lindsley CW, Weaver CD, Swale DR. Use of chemical probes to explore the toxicological potential of the K +/Cl - cotransporter (KCC) as a novel insecticide target to control the primary vector of dengue and Zika virus, Aedes aegypti. Pestic Biochem Physiol 2018; 151:10-17. [PMID: 30704707 DOI: 10.1016/j.pestbp.2018.03.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/16/2018] [Accepted: 03/29/2018] [Indexed: 06/09/2023]
Abstract
The majority of commercialized insecticides target the insect nervous system and therefore, neural proteins are well-validated targets for insecticide development. Considering that only a few neural targets are exploited for insecticidal action and the development of insecticide resistance has reduced the efficacy of current insecticidal classes, we sought to test the toxicological potential of the potassium-chloride cotransporter (KCC). In mammals, KCC proteins have seminal roles in shaping GABAergic signaling and inhibitory neurotransmission, thus ion transport through KCC is critical for proper neurotransmission. Therefore, we hypothesized that mosquito KCC represents a putative insecticide target site and that pharmacological inhibition of KCC constructs in Aedes aegypti will be lethal. To test this hypothesis, we developed a robust, cell-based fluorescence assay that enables in vitro characterization of small-molecules against Ae. aegypti KCC and performed a proof-of-concept study employing well characterized mammalian KCC modulators to determine the toxicological potential of Ae. aegypti KCC. The selective inhibitor of mammalian KCC, termed VU0463271, was found to be a potent inhibitor Ae. aegypti KCC and microinjection induced lethality in a concentration-dependent manner to susceptible and pyrethroid resistant strains. Importantly, an analog of VU0463271 was shown to be >40-fold less potent and did not induce toxicity, suggesting that the observed physiological effects and mortality are likely due to KCC inhibition. This proof-of-concept study suggests that Ae. aegypti KCC represents a putative target site for mosquitocide design that can mitigate the current mechanisms of insecticide resistance.
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Affiliation(s)
- Francis J Prael
- Vanderbilt University School of Medicine, Department of Pharmacology, Nashville, TN 37232, United States; Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Nashville, TN 37232, United States
| | - Rui Chen
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States
| | - Zhilin Li
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States
| | - Carson W Reed
- Vanderbilt University School of Medicine, Department of Pharmacology, Nashville, TN 37232, United States; Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Nashville, TN 37232, United States; Vanderbilt Center for Neuroscience Drug Discovery, Nashville, TN 37232, United States
| | - Craig W Lindsley
- Vanderbilt University School of Medicine, Department of Pharmacology, Nashville, TN 37232, United States; Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Nashville, TN 37232, United States; Vanderbilt Center for Neuroscience Drug Discovery, Nashville, TN 37232, United States
| | - C David Weaver
- Vanderbilt University School of Medicine, Department of Pharmacology, Nashville, TN 37232, United States; Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Nashville, TN 37232, United States; Vanderbilt Center for Neuroscience Drug Discovery, Nashville, TN 37232, United States
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States.
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Carrington SJ, Hernandez CC, Swale DR, Aluko OA, Denton JS, Cone RD. G protein-coupled receptors differentially regulate glycosylation and activity of the inwardly rectifying potassium channel Kir7.1. J Biol Chem 2018; 293:17739-17753. [PMID: 30257863 DOI: 10.1074/jbc.ra118.003238] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 09/18/2018] [Indexed: 12/15/2022] Open
Abstract
Kir7.1 is an inwardly rectifying potassium channel with important roles in the regulation of the membrane potential in retinal pigment epithelium, uterine smooth muscle, and hypothalamic neurons. Regulation of G protein-coupled inwardly rectifying potassium (GIRK) channels by G protein-coupled receptors (GPCRs) via the G protein βγ subunits has been well characterized. However, how Kir channels are regulated is incompletely understood. We report here that Kir7.1 is also regulated by GPCRs, but through a different mechanism. Using Western blotting analysis, we observed that multiple GPCRs tested caused a striking reduction in the complex glycosylation of Kir7.1. Further, GPCR-mediated reduction of Kir7.1 glycosylation in HEK293T cells did not alter its expression at the cell surface but decreased channel activity. Of note, mutagenesis of the sole Kir7.1 glycosylation site reduced conductance and open probability, as indicated by single-channel recording. Additionally, we report that the L241P mutation of Kir7.1 associated with Lebers congenital amaurosis (LCA), an inherited retinal degenerative disease, has significantly reduced complex glycosylation. Collectively, these results suggest that Kir7.1 channel glycosylation is essential for function, and this activity within cells is suppressed by most GPCRs. The melanocortin-4 receptor (MC4R), a GPCR previously reported to induce ligand-regulated activity of this channel, is the only GPCR tested that does not have this effect on Kir7.1.
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Affiliation(s)
- Sheridan J Carrington
- From the Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232; Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | - Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, Louisiana 70803
| | - Oluwatosin A Aluko
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | - Jerod S Denton
- Departments of Anesthesiology; Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Roger D Cone
- From the Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232; Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109; Department of Molecular and Integrative Physiology, University of Michigan School of Medicine, Ann Arbor, Michigan 48109.
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Sparks JT, Botsko G, Swale DR, Boland LM, Patel SS, Dickens JC. Membrane Proteins Mediating Reception and Transduction in Chemosensory Neurons in Mosquitoes. Front Physiol 2018; 9:1309. [PMID: 30294282 PMCID: PMC6158332 DOI: 10.3389/fphys.2018.01309] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 08/30/2018] [Indexed: 12/17/2022] Open
Abstract
Mosquitoes use chemical cues to modulate important behaviors such as feeding, mating, and egg laying. The primary chemosensory organs comprising the paired antennae, maxillary palps and labial palps are adorned with porous sensilla that house primary sensory neurons. Dendrites of these neurons provide an interface between the chemical environment and higher order neuronal processing. Diverse proteins located on outer membranes interact with chemicals, ions, and soluble proteins outside the cell and within the lumen of sensilla. Here, we review the repertoire of chemosensory receptors and other membrane proteins involved in transduction and discuss the outlook for their functional characterization. We also provide a brief overview of select ion channels, their role in mammalian taste, and potential involvement in mosquito taste. These chemosensory proteins represent targets for the disruption of harmful biting behavior and disease transmission by mosquito vectors.
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Affiliation(s)
- Jackson T Sparks
- Biology Department, High Point University, High Point, NC, United States
| | - Gina Botsko
- Biology Department, High Point University, High Point, NC, United States
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, United States
| | - Linda M Boland
- Department of Biology, University of Richmond, Richmond, VA, United States
| | - Shriraj S Patel
- Department of Biology, University of Richmond, Richmond, VA, United States
| | - Joseph C Dickens
- Department of Biology, University of Richmond, Richmond, VA, United States
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Holderman CJ, Swale DR, Bloomquist JR, Kaufman PE. Resistance to Permethrin, β-cyfluthrin, and Diazinon in Florida Horn Fly Populations. Insects 2018; 9:insects9020063. [PMID: 29895770 PMCID: PMC6023543 DOI: 10.3390/insects9020063] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/25/2018] [Accepted: 06/07/2018] [Indexed: 11/16/2022]
Abstract
Horn flies, Haematobia irritans, a major cattle pest in the USA, cause substantial economic losses and current control methods rely heavily on insecticides. Three horn fly populations were evaluated for insecticide susceptibility to permethrin, β-cyfluthrin, and diazinon. Susceptibility was variable by population, with the greatest resistance exhibited by a 66-fold resistance ratio (RR) to permethrin and >14-fold RR to diazinon. Mechanisms of resistance were determined using molecular techniques and enzymatic assays. The knockdown resistance (kdr) genotype (L150F) associated with pyrethroid resistance, and a G262A mutation in acetylcholinesterase, previously associated with organophosphate resistance, were found in all field populations evaluated. Insensitivity of diazoxon at the acetylcholinesterase (AChE) target site was significantly different in horn flies from one of the field sites. For metabolic detoxifying enzymes, cytochrome P450 nor general esterases showed a significant difference between field strains and a laboratory susceptible strain. Pyrethroid resistance was likely due to the presence of the L150F mutation in the population. In vitro studies targeting the AChE enzyme did not support the notion that the G262A mutation was the sole cause of resistance to organophosphates, and, therefore, the exact resistance mechanism to diazinon was not able to be confirmed.
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Affiliation(s)
- Chris J Holderman
- Entomology and Nematology Department, University of Florida, Gainesville, FL 32611, USA.
| | - Daniel R Swale
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
| | - Jeffery R Bloomquist
- Entomology and Nematology Department, University of Florida, Gainesville, FL 32611, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA.
| | - Phillip E Kaufman
- Entomology and Nematology Department, University of Florida, Gainesville, FL 32611, USA.
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Swale DR, Li Z, Kraft JZ, Healy K, Liu M, David CM, Liu Z, Foil LD. Development of an autodissemination strategy for the deployment of novel control agents targeting the common malaria mosquito, Anopheles quadrimaculatus say (Diptera: Culicidae). PLoS Negl Trop Dis 2018; 12:e0006259. [PMID: 29641515 PMCID: PMC5894962 DOI: 10.1371/journal.pntd.0006259] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 01/22/2018] [Indexed: 12/14/2022] Open
Abstract
Background The reduced efficacy of current Anopheline mosquito control methods underscores the need to develop new methods of control that exploit unique target sites and/or utilizes novel deployment methods. Autodissemination methodologies using insect growth regulators (IGRs) is growing in interest and has been shown to be effective at controlling Aedes mosquitoes in semi-field and field environments, yet little information exists for Anopheline mosquitoes. Therefore, we tested the hypothesis that female-driven autodissemination of an IGR combined with a new mechanism of action insecticide (Kir channel inhibitor) could be employed to reduce Anopheline populations. Methodology We studied the ability of three IGRs to be transferred to the larval habitat during oviposition in laboratory and semi-field environments. Adult mosquitoes were exposed to the chemicals for 4 hours immediately after blood feeding and efficacy was tested using classical methodologies, including adult emergence inhibition and High Performance Liquid Chromatography (HPLC). A complete autodissemination design was tested in a semi-field environment. Principal findings Larval survivability and adult emergence were significantly reduced in habitats that were visited by novaluron treated adults, but no statistical differences were observed with pyriproxyfen or triflumuron. These data suggested novaluron, but not pyriproxyfen or triflumuron, was horizontally transferred from the adult mosquito to the larval habitat during oviposition. HPLC studies supported the toxicity data and showed that novaluron was present in the majority of larval habitats, suggesting that novaluron can be horizontally transferred by Anopheles quadrimaculatus. Importantly, the combination of novaluron and the Kir channel inhibitor, VU041, was capable of reducing adult and larval populations in semi-field environments. Conclusions Novaluron can be transferred to the adult at a greater efficacy and/or is not degraded as quickly during the gonotropic cycle when compared to pyriproxyfen or triflumuron. Pending field confirmation, autodissemination approaches with novaluron may be a suitable tool to manage Anopheles populations. Efforts to control the mosquito vector of malaria, Anopheles gambiae, have been dominated by the use of insecticide-treated bednets or residual spraying efforts for the previous 2–3 decades. The persistent use of these methods has led to a decline in control efficacy and has highlighted the need to 1) identify novel molecular targets and 2) novel translational deployment methods to control mosquito vectors. To address this, we employed biological and chemical methods to test the hypothesis that insect growth regulators (IGR) are capable of being transferred to an oviposition site at lethal concentrations when Anopheles adults are exposed immediately after blood feeding. Subsequently, we tested the hypothesis that K+ channel modulators and an IGR used in combination will reduce the mosquito population in a semi-field environment through adult toxicity and IGR transfer. The data presented in this study provides a proof-of-concept that autodissemination methods using specific IGRs and K+ channel modulators are potentially capable of reducing the burden of malaria through a method that is novel, cost efficient, long lasting, and requires minimal human intervention.
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Affiliation(s)
- Daniel R. Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, United States of America
- * E-mail:
| | - Zhilin Li
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, United States of America
| | - Jake Z. Kraft
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, United States of America
| | - Kristen Healy
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, United States of America
| | - Mei Liu
- Louisiana State University AgCenter, School of Renewable Natural Resources, Baton Rouge, LA, United States of America
| | - Connie M. David
- Louisiana State University, Department of Chemistry, Baton Rouge, LA, United States of America
| | - Zhijun Liu
- Louisiana State University AgCenter, School of Renewable Natural Resources, Baton Rouge, LA, United States of America
| | - Lane D. Foil
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, United States of America
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Chen R, Swale DR. Inwardly Rectifying Potassium (Kir) Channels Represent a Critical Ion Conductance Pathway in the Nervous Systems of Insects. Sci Rep 2018; 8:1617. [PMID: 29371678 PMCID: PMC5785497 DOI: 10.1038/s41598-018-20005-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/10/2018] [Indexed: 12/13/2022] Open
Abstract
A complete understanding of the physiological pathways critical for proper function of the insect nervous system is still lacking. The recent development of potent and selective small-molecule modulators of insect inward rectifier potassium (Kir) channels has enabled the interrogation of the physiological role and toxicological potential of Kir channels within various insect tissue systems. Therefore, we aimed to highlight the physiological and functional role of neural Kir channels the central nervous system, muscular system, and neuromuscular system through pharmacological and genetic manipulations. Our data provide significant evidence that Drosophila neural systems rely on the inward conductance of K+ ions for proper function since pharmacological inhibition and genetic ablation of neural Kir channels yielded dramatic alterations of the CNS spike discharge frequency and broadening and reduced amplitude of the evoked EPSP at the neuromuscular junction. Based on these data, we conclude that neural Kir channels in insects (1) are critical for proper function of the insect nervous system, (2) represents an unexplored physiological pathway that is likely to shape the understanding of neuronal signaling, maintenance of membrane potentials, and maintenance of the ionic balance of insects, and (3) are capable of inducing acute toxicity to insects through neurological poisoning.
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Affiliation(s)
- Rui Chen
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, 70803, USA
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA, 70803, USA.
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Swale DR, Li Z, Guerrero F, Pérez De León AA, Foil LD. Role of inward rectifier potassium channels in salivary gland function and sugar feeding of the fruit fly, Drosophila melanogaster. Pestic Biochem Physiol 2017; 141:41-49. [PMID: 28911739 DOI: 10.1016/j.pestbp.2016.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/11/2016] [Accepted: 11/14/2016] [Indexed: 06/07/2023]
Abstract
The arthropod salivary gland is of critical importance for horizontal transmission of pathogens, yet a detailed understanding of the ion conductance pathways responsible for saliva production and excretion is lacking. A superfamily of potassium ion channels, known as inward rectifying potassium (Kir) channels, is overexpressed in the Drosophila salivary gland by 32-fold when compared to the whole body mRNA transcripts. Therefore, we aimed to test the hypothesis that pharmacological and genetic depletion of salivary gland specific Kir channels alters the efficiency of the gland and reduced feeding capabilities using the fruit fly Drosophila melanogaster as a model organism that could predict similar effects in arthropod disease vectors. Exposure to VU041, a selective Kir channel blocker, reduced the volume of sucrose consumption by up to 3.2-fold and was found to be concentration-dependent with an EC50 of 68μM. Importantly, the inactive analog, VU937, was shown to not influence feeding, suggesting the reduction in feeding observed with VU041 is due to Kir channel inhibition. Next, we performed a salivary gland specific knockdown of Kir1 to assess the role of these channels specifically in the salivary gland. The genetically depleted fruit flies had a reduction in total volume ingested and an increase in the time spent feeding, both suggestive of a reduction in salivary gland function. Furthermore, a compensatory mechanism appears to be present at day 1 of RNAi-treated fruit flies, and is likely to be the Na+-K+-2Cl- cotransporter and/or Na+-K+-ATPase pumps that serve to supplement the inward flow of K+ ions, which highlights the functional redundancy in control of ion flux in the salivary glands. These findings suggest that Kir channels likely provide, at least in part, a principal potassium conductance pathway in the Drosophila salivary gland that is required for sucrose feeding.
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Affiliation(s)
- Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States.
| | - Zhilin Li
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States
| | - Felix Guerrero
- United States Department of Agriculture-Agricultural Research Service, Knipling-Bushland United States Livestock Insects Research Laboratory, Veterinary Pest Genomics Center, 2700 Fredericksburg Rd., Kerrville, TX 78028, United States
| | - Adalberto A Pérez De León
- United States Department of Agriculture-Agricultural Research Service, Knipling-Bushland United States Livestock Insects Research Laboratory, Veterinary Pest Genomics Center, 2700 Fredericksburg Rd., Kerrville, TX 78028, United States
| | - Lane D Foil
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States
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O'Neal ST, Swale DR, Anderson TD. ATP-sensitive inwardly rectifying potassium channel regulation of viral infections in honey bees. Sci Rep 2017; 7:8668. [PMID: 28819165 PMCID: PMC5561242 DOI: 10.1038/s41598-017-09448-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 07/26/2017] [Indexed: 12/24/2022] Open
Abstract
Honey bees are economically important pollinators of a wide variety of crops that have attracted the attention of both researchers and the public alike due to unusual declines in the numbers of managed colonies in some parts of the world. Viral infections are thought to be a significant factor contributing to these declines, but viruses have proven a challenging pathogen to study in a bee model and interactions between viruses and the bee antiviral immune response remain poorly understood. In the work described here, we have demonstrated the use of flock house virus (FHV) as a model system for virus infection in bees and revealed an important role for the regulation of the bee antiviral immune response by ATP-sensitive inwardly rectifying potassium (KATP) channels. We have shown that treatment with the KATP channel agonist pinacidil increases survival of bees while decreasing viral replication following infection with FHV, whereas treatment with the KATP channel antagonist tolbutamide decreases survival and increases viral replication. Our results suggest that KATP channels provide a significant link between cellular metabolism and the antiviral immune response in bees.
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Affiliation(s)
- Scott T O'Neal
- Department of Entomology, Virginia Tech, Blacksburg, VA, USA.
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Troy D Anderson
- Department of Entomology, University of Nebraska, Lincoln, NE, USA.
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O'Neal ST, Swale DR, Bloomquist JR, Anderson TD. ATP-sensitive inwardly rectifying potassium channel modulators alter cardiac function in honey bees. J Insect Physiol 2017; 99:95-100. [PMID: 28412203 DOI: 10.1016/j.jinsphys.2017.04.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 04/06/2017] [Accepted: 04/11/2017] [Indexed: 06/07/2023]
Abstract
ATP-sensitive inwardly rectifying potassium (KATP) channels couple cellular metabolism to the membrane potential of the cell and play an important role in a variety of tissue types, including the insect dorsal vessel, making them a subject of interest not only for understanding invertebrate physiology, but also as a potential target for novel insecticides. Most of what is known about these ion channels is the result of work performed in mammalian systems, with insect studies being limited to only a few species and physiological systems. The goal of this study was to investigate the role that KATP channels play in regulating cardiac function in a model social insect, the honey bee (Apis mellifera), by examining the effects that modulators of these ion channels have on heart rate. Heart rate decreased in a concentration-dependent manner, relative to controls, with the application of the KATP channel antagonist tolbutamide and KATP channel blockers barium and magnesium, whereas heart rate increased with the application of a low concentration of the KATP channel agonist pinacidil, but decreased at higher concentrations. Furthermore, pretreatment with barium magnified the effects of tolbutamide treatment and eliminated the effects of pinacidil treatment at select concentrations. The data presented here confirm a role for KATP channels in the regulation of honey bee dorsal vessel contractions and provide insight into the underlying physiology that governs the regulation of bee cardiac function.
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Affiliation(s)
- Scott T O'Neal
- Department of Entomology, Virginia Tech, Blacksburg, VA, USA.
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, USA
| | - Jeffrey R Bloomquist
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Troy D Anderson
- Department of Entomology, University of Nebraska, Lincoln, NE, USA
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Swale DR, Engers DW, Bollinger SR, Gross A, Inocente EA, Days E, Kanga F, Johnson RM, Yang L, Bloomquist JR, Hopkins CR, Piermarini PM, Denton JS. An insecticide resistance-breaking mosquitocide targeting inward rectifier potassium channels in vectors of Zika virus and malaria. Sci Rep 2016; 6:36954. [PMID: 27849039 PMCID: PMC5111108 DOI: 10.1038/srep36954] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 10/19/2016] [Indexed: 01/01/2023] Open
Abstract
Insecticide resistance is a growing threat to mosquito control programs around the world, thus creating the need to discover novel target sites and target-specific compounds for insecticide development. Emerging evidence suggests that mosquito inward rectifier potassium (Kir) channels represent viable molecular targets for developing insecticides with new mechanisms of action. Here we describe the discovery and characterization of VU041, a submicromolar-affinity inhibitor of Anopheles (An.) gambiae and Aedes (Ae.) aegypti Kir1 channels that incapacitates adult female mosquitoes from representative insecticide-susceptible and -resistant strains of An. gambiae (G3 and Akron, respectively) and Ae. aegypti (Liverpool and Puerto Rico, respectively) following topical application. VU041 is selective for mosquito Kir channels over several mammalian orthologs, with the exception of Kir2.1, and is not lethal to honey bees. Medicinal chemistry was used to develop an analog, termed VU730, which retains activity toward mosquito Kir1 but is not active against Kir2.1 or other mammalian Kir channels. Thus, VU041 and VU730 are promising chemical scaffolds for developing new classes of insecticides to combat insecticide-resistant mosquitoes and the transmission of mosquito-borne diseases, such as Zika virus, without harmful effects on humans and beneficial insects.
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Affiliation(s)
- Daniel R Swale
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Darren W Engers
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Sean R Bollinger
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Aaron Gross
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Edna Alfaro Inocente
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Emily Days
- Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Fariba Kanga
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Reed M Johnson
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Liu Yang
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Jeffrey R Bloomquist
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Corey R Hopkins
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Jerod S Denton
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Institute for Global Health, Vanderbilt University, Nashville, TN 37203, USA
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Swale DR, Kurata H, Kharade SV, Sheehan J, Raphemot R, Voigtritter KR, Figueroa EE, Meiler J, Blobaum AL, Lindsley CW, Hopkins CR, Denton JS. ML418: The First Selective, Sub-Micromolar Pore Blocker of Kir7.1 Potassium Channels. ACS Chem Neurosci 2016; 7:1013-23. [PMID: 27184474 DOI: 10.1021/acschemneuro.6b00111] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The inward rectifier potassium (Kir) channel Kir7.1 (KCNJ13) has recently emerged as a key regulator of melanocortin signaling in the brain, electrolyte homeostasis in the eye, and uterine muscle contractility during pregnancy. The pharmacological tools available for exploring the physiology and therapeutic potential of Kir7.1 have been limited to relatively weak and nonselective small-molecule inhibitors. Here, we report the discovery in a fluorescence-based high-throughput screen of a novel Kir7.1 channel inhibitor, VU714. Site-directed mutagenesis of pore-lining amino acid residues identified glutamate 149 and alanine 150 as essential determinants of VU714 activity. Lead optimization with medicinal chemistry generated ML418, which exhibits sub-micromolar activity (IC50 = 310 nM) and superior selectivity over other Kir channels (at least 17-fold selective over Kir1.1, Kir2.1, Kir2.2, Kir2.3, Kir3.1/3.2, and Kir4.1) except for Kir6.2/SUR1 (equally potent). Evaluation in the EuroFins Lead Profiling panel of 64 GPCRs, ion-channels, and transporters for off-target activity of ML418 revealed a relatively clean ancillary pharmacology. While ML418 exhibited low CLHEP in human microsomes which could be modulated with lipophilicity adjustments, it showed high CLHEP in rat microsomes regardless of lipophilicity. A subsequent in vivo PK study of ML418 by intraperitoneal (IP) administration (30 mg/kg dosage) revealed a suitable PK profile (Cmax = 0.20 μM and Tmax = 3 h) and favorable CNS distribution (mouse brain/plasma Kp of 10.9 to support in vivo studies. ML418, which represents the current state-of-the-art in Kir7.1 inhibitors, should be useful for exploring the physiology of Kir7.1 in vitro and in vivo.
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Affiliation(s)
| | | | | | - Jonathan Sheehan
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37232, United States
| | | | | | | | - Jens Meiler
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37232, United States
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Affiliation(s)
- Sujay V Kharade
- a Department of Anesthesiology ; Vanderbilt University Medical Center ; Nashville , TN USA
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Swale DR, Sheehan JH, Banerjee S, Husni AS, Nguyen TT, Meiler J, Denton JS. Computational and functional analyses of a small-molecule binding site in ROMK. Biophys J 2016; 108:1094-103. [PMID: 25762321 DOI: 10.1016/j.bpj.2015.01.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 01/21/2015] [Accepted: 01/23/2015] [Indexed: 12/20/2022] Open
Abstract
The renal outer medullary potassium channel (ROMK, or Kir1.1, encoded by KCNJ1) critically regulates renal tubule electrolyte and water transport and hence blood volume and pressure. The discovery of loss-of-function mutations in KCNJ1 underlying renal salt and water wasting and lower blood pressure has sparked interest in developing new classes of antihypertensive diuretics targeting ROMK. The recent development of nanomolar-affinity small-molecule inhibitors of ROMK creates opportunities for exploring the chemical and physical basis of ligand-channel interactions required for selective ROMK inhibition. We previously reported that the bis-nitro-phenyl ROMK inhibitor VU591 exhibits voltage-dependent knock-off at hyperpolarizing potentials, suggesting that the binding site is located within the ion-conduction pore. In this study, comparative molecular modeling and in silico ligand docking were used to interrogate the full-length ROMK pore for energetically favorable VU591 binding sites. Cluster analysis of 2498 low-energy poses resulting from 9900 Monte Carlo docking trajectories on each of 10 conformationally distinct ROMK comparative homology models identified two putative binding sites in the transmembrane pore that were subsequently tested for a role in VU591-dependent inhibition using site-directed mutagenesis and patch-clamp electrophysiology. Introduction of mutations into the lower site had no effect on the sensitivity of the channel to VU591. In contrast, mutations of Val(168) or Asn(171) in the upper site, which are unique to ROMK within the Kir channel family, led to a dramatic reduction in VU591 sensitivity. This study highlights the utility of computational modeling for defining ligand-ROMK interactions and proposes a mechanism for inhibition of ROMK.
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Affiliation(s)
- Daniel R Swale
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jonathan H Sheehan
- Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Biochemistry, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Sreedatta Banerjee
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Afeef S Husni
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Thuy T Nguyen
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jens Meiler
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee; Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jerod S Denton
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee; Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, Tennessee; Institute for Global Health, Vanderbilt University Medical Center, Nashville, Tennessee.
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Herington JL, Swale DR, Brown N, Shelton EL, Choi H, Williams CH, Hong CC, Paria BC, Denton JS, Reese J. High-Throughput Screening of Myometrial Calcium-Mobilization to Identify Modulators of Uterine Contractility. PLoS One 2015; 10:e0143243. [PMID: 26600013 PMCID: PMC4658040 DOI: 10.1371/journal.pone.0143243] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Accepted: 11/02/2015] [Indexed: 12/27/2022] Open
Abstract
The uterine myometrium (UT-myo) is a therapeutic target for preterm labor, labor induction, and postpartum hemorrhage. Stimulation of intracellular Ca2+-release in UT-myo cells by oxytocin is a final pathway controlling myometrial contractions. The goal of this study was to develop a dual-addition assay for high-throughput screening of small molecular compounds, which could regulate Ca2+-mobilization in UT-myo cells, and hence, myometrial contractions. Primary murine UT-myo cells in 384-well plates were loaded with a Ca2+-sensitive fluorescent probe, and then screened for inducers of Ca2+-mobilization and inhibitors of oxytocin-induced Ca2+-mobilization. The assay exhibited robust screening statistics (Z´ = 0.73), DMSO-tolerance, and was validated for high-throughput screening against 2,727 small molecules from the Spectrum, NIH Clinical I and II collections of well-annotated compounds. The screen revealed a hit-rate of 1.80% for agonist and 1.39% for antagonist compounds. Concentration-dependent responses of hit-compounds demonstrated an EC50 less than 10μM for 21 hit-antagonist compounds, compared to only 7 hit-agonist compounds. Subsequent studies focused on hit-antagonist compounds. Based on the percent inhibition and functional annotation analyses, we selected 4 confirmed hit-antagonist compounds (benzbromarone, dipyridamole, fenoterol hydrobromide and nisoldipine) for further analysis. Using an ex vivo isometric contractility assay, each compound significantly inhibited uterine contractility, at different potencies (IC50). Overall, these results demonstrate for the first time that high-throughput small-molecules screening of myometrial Ca2+-mobilization is an ideal primary approach for discovering modulators of uterine contractility.
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Affiliation(s)
- Jennifer L. Herington
- Department of Pediatrics, Division of Neonatology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
| | - Daniel R. Swale
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, United States of America
| | - Naoko Brown
- Department of Pediatrics, Division of Neonatology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Elaine L. Shelton
- Department of Pediatrics, Division of Neonatology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Hyehun Choi
- Department of Pediatrics, Division of Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Charles H. Williams
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Charles C. Hong
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Bibhash C. Paria
- Department of Pediatrics, Division of Neonatology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Jerod S. Denton
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Jeff Reese
- Department of Pediatrics, Division of Neonatology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
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Swale DR, Carlier PR, Hartsel JA, Ma M, Bloomquist JR. Mosquitocidal carbamates with low toxicity to agricultural pests: an advantageous property for insecticide resistance management. Pest Manag Sci 2015; 71:1158-64. [PMID: 25185896 PMCID: PMC4348351 DOI: 10.1002/ps.3899] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/31/2014] [Accepted: 08/29/2014] [Indexed: 05/10/2023]
Abstract
BACKGROUND Insecticide resistance in the malaria mosquito Anopheles gambiae is well documented, and widespread agricultural use of pyrethroids may exacerbate development of resistance when pyrethroids are used in vector control. We have developed carbamate anticholinesterases that possess a high degree of An. gambiae:human selectivity for enzyme inhibition. The purpose of this study was to assess the spectrum of activity of these carbamates against other mosquitoes and agricultural pests. RESULTS Experimental carbamates were potent inhibitors of mosquito acetylcholinesterases, with IC50 values in the nanomolar range. Similar potencies were observed for Musca domestica and Drosophila melanogaster enzymes. Although meta-substituted carbamates were potent inhibitors, two ortho-substituted carbamates displayed poor enzyme inhibition (IC50 ≥ 10(-6) M) in honey bee (Apis mellifera), Asian citrus psyllid (Diaphorina citri) and lepidopteran agricultural pests (Plutella xylostella and Ostrinia nubilalis). Enzyme inhibition results were confirmed by toxicity studies in caterpillars, where the new carbamates were 2-3-fold less toxic than propoxur and up to tenfold less active than bendiocarb, indicating little utility of these compounds for crop protection. CONCLUSION The experimental carbamates were broadly active against mosquito species but not agricultural pests, which should mitigate selection for mosquito insecticide resistance by reducing agricultural uses of these compounds. © 2014 Society of Chemical Industry.
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Affiliation(s)
- Daniel R. Swale
- University of Florida, Department of Entomology and Nematology, Emerging Pathogens Institute, Gainesville, FL, 32611, USA
| | - Paul R. Carlier
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA
| | - Joshua A. Hartsel
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA
| | - Ming Ma
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA
| | - Jeffrey R. Bloomquist
- University of Florida, Department of Entomology and Nematology, Emerging Pathogens Institute, Gainesville, FL, 32611, USA
- Corresponding Author: Jeffrey R. Bloomquist, Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32610, USA, Phone: (352) 273-9417 (office), (352) 273-9420 (fax),
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Mutunga JM, Anderson TD, Craft DT, Gross AD, Swale DR, Tong F, Wong DM, Carlier PR, Bloomquist JR. Carbamate and pyrethroid resistance in the akron strain of Anopheles gambiae. Pestic Biochem Physiol 2015; 121:116-121. [PMID: 26047119 PMCID: PMC4457939 DOI: 10.1016/j.pestbp.2015.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 03/02/2015] [Accepted: 03/03/2015] [Indexed: 06/04/2023]
Abstract
Insecticide resistance in the malaria vector, Anopheles gambiae, is a serious problem, epitomized by the multi-resistant Akron strain, originally isolated in the country of Benin. Here we report resistance in this strain to pyrethroids and DDT (13-fold to 35-fold compared to the susceptible G3 strain), but surprisingly little resistance to etofenprox, a compound sometimes described as a "pseudo-pyrethroid." There was also strong resistance to topically-applied commercial carbamates (45-fold to 81-fold), except for the oximes aldicarb and methomyl. Biochemical assays showed enhanced cytochrome P450 monooxygenase and carboxylesterase activity, but not that of glutathione-S-transferase. A series of substituted α,α,α,-trifluoroacetophenone oxime methylcarbamates were evaluated for enzyme inhibition potency and toxicity against G3 and Akron mosquitoes. The compound bearing an unsubstituted phenyl ring showed the greatest toxicity to mosquitoes of both strains. Low cross resistance in Akron was retained by all analogs in the series. Kinetic analysis of acetylcholinesterase activity and its inhibition by insecticides in the G3 strain showed inactivation rate constants greater than that of propoxur, and against Akron enzyme inactivation rate constants similar to that of aldicarb. However, inactivation rate constants against recombinant human AChE were essentially identical to that of the G3 strain. Thus, the acetophenone oxime carbamates described here, though potent insecticides that control resistant Akron mosquitoes, require further structural modification to attain acceptable selectivity and human safety.
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Affiliation(s)
- James M Mutunga
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Troy D Anderson
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Derek T Craft
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Aaron D Gross
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Daniel R Swale
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Fan Tong
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Dawn M Wong
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Paul R Carlier
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA.
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Raphemot R, Rouhier MF, Swale DR, Days E, Weaver CD, Lovell KM, Konkel LC, Engers DW, Bollinger SF, Hopkins C, Piermarini PM, Denton JS. Discovery and characterization of a potent and selective inhibitor of Aedes aegypti inward rectifier potassium channels. PLoS One 2014; 9:e110772. [PMID: 25375326 PMCID: PMC4222822 DOI: 10.1371/journal.pone.0110772] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/16/2014] [Indexed: 12/12/2022] Open
Abstract
Vector-borne diseases such as dengue fever and malaria, which are transmitted by infected female mosquitoes, affect nearly half of the world's population. The emergence of insecticide-resistant mosquito populations is reducing the effectiveness of conventional insecticides and threatening current vector control strategies, which has created an urgent need to identify new molecular targets against which novel classes of insecticides can be developed. We previously demonstrated that small molecule inhibitors of mammalian Kir channels represent promising chemicals for new mosquitocide development. In this study, high-throughput screening of approximately 30,000 chemically diverse small-molecules was employed to discover potent and selective inhibitors of Aedes aegypti Kir1 (AeKir1) channels heterologously expressed in HEK293 cells. Of 283 confirmed screening ‘hits’, the small-molecule inhibitor VU625 was selected for lead optimization and in vivo studies based on its potency and selectivity toward AeKir1, and tractability for medicinal chemistry. In patch clamp electrophysiology experiments of HEK293 cells, VU625 inhibits AeKir1 with an IC50 value of 96.8 nM, making VU625 the most potent inhibitor of AeKir1 described to date. Furthermore, electrophysiology experiments in Xenopus oocytes revealed that VU625 is a weak inhibitor of AeKir2B. Surprisingly, injection of VU625 failed to elicit significant effects on mosquito behavior, urine excretion, or survival. However, when co-injected with probenecid, VU625 inhibited the excretory capacity of mosquitoes and was toxic, suggesting that the compound is a substrate of organic anion and/or ATP-binding cassette (ABC) transporters. The dose-toxicity relationship of VU625 (when co-injected with probenecid) is biphasic, which is consistent with the molecule inhibiting both AeKir1 and AeKir2B with different potencies. This study demonstrates proof-of-concept that potent and highly selective inhibitors of mosquito Kir channels can be developed using conventional drug discovery approaches. Furthermore, it reinforces the notion that the physical and chemical properties that determine a compound's bioavailability in vivo will be critical in determining the efficacy of Kir channel inhibitors as insecticides.
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Affiliation(s)
- Rene Raphemot
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - Matthew F. Rouhier
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, United States of America
| | - Daniel R. Swale
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Emily Days
- Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - C. David Weaver
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - Kimberly M. Lovell
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Leah C. Konkel
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Darren W. Engers
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Sean F. Bollinger
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Corey Hopkins
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute for Global Health, Vanderbilt University, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Peter M. Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, United States of America
- * E-mail: (PMP); (JSD)
| | - Jerod S. Denton
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute for Global Health, Vanderbilt University, Nashville, TN, United States of America
- * E-mail: (PMP); (JSD)
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Abstract
Recent studies suggest that N, N-diethyl-meta-toluamide (DEET) is an acetylcholinesterase inhibitor and that this action may result in neurotoxicity and pose a risk to humans from its use as an insect repellent. We investigated the mode of action of DEET neurotoxicity in order to define the specific neuronal targets related to its acute toxicity in insects and mammals. Although toxic to mosquitoes (LD50 ca. 1.5 µg/mg), DEET was a poor acetylcholinesterase inhibitor (<10% inhibition), even at a concentration of 10 mM. IC50 values for DEET against Drosophila melanogaster, Musca domestica, and human acetylcholinesterases were 6–12 mM. Neurophysiological recordings showed that DEET had excitatory effects on the housefly larval central nervous system (EC50: 120 µM), but was over 300-fold less potent than propoxur, a standard anticholinesterase insecticide. Phentolamine, an octopamine receptor antagonist, completely blocked the central neuroexcitation by DEET and octopamine, but was essentially ineffective against hyperexcitation by propoxur and 4-aminopyridine, a potassium channel blocker. DEET was found to illuminate the firefly light organ, a tissue utilizing octopamine as the principal neurotransmitter. Additionally, DEET was shown to increase internal free calcium via the octopamine receptors of Sf21 cells, an effect blocked by phentolamine. DEET also blocked Na+ and K+ channels in patch clamped rat cortical neurons, with IC50 values in the micromolar range. These findings suggest DEET is likely targeting octopaminergic synapses to induce neuroexcitation and toxicity in insects, while acetylcholinesterase in both insects and mammals has low (mM) sensitivity to DEET. The ion channel blocking action of DEET in neurons may contribute to the numbness experienced after inadvertent application to the lips or mouth of humans.
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Affiliation(s)
- Daniel R. Swale
- University of Florida, Emerging Pathogens Institute, Department of Entomology and Nematology, Gainesville, Florida, United States of America
| | - Baonan Sun
- University of Florida, Emerging Pathogens Institute, Department of Entomology and Nematology, Gainesville, Florida, United States of America
| | - Fan Tong
- University of Florida, Emerging Pathogens Institute, Department of Entomology and Nematology, Gainesville, Florida, United States of America
| | - Jeffrey R. Bloomquist
- University of Florida, Emerging Pathogens Institute, Department of Entomology and Nematology, Gainesville, Florida, United States of America
- * E-mail:
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45
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Raphemot R, Swale DR, Dadi PK, Jacobson DA, Cooper P, Wojtovich AP, Banerjee S, Nichols CG, Denton JS. Direct activation of β-cell KATP channels with a novel xanthine derivative. Mol Pharmacol 2014; 85:858-65. [PMID: 24646456 DOI: 10.1124/mol.114.091884] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
ATP-regulated potassium (KATP) channel complexes of inward rectifier potassium channel (Kir) 6.2 and sulfonylurea receptor (SUR) 1 critically regulate pancreatic islet β-cell membrane potential, calcium influx, and insulin secretion, and consequently, represent important drug targets for metabolic disorders of glucose homeostasis. The KATP channel opener diazoxide is used clinically to treat intractable hypoglycemia caused by excessive insulin secretion, but its use is limited by off-target effects due to lack of potency and selectivity. Some progress has been made in developing improved Kir6.2/SUR1 agonists from existing chemical scaffolds and compound screening, but there are surprisingly few distinct chemotypes that are specific for SUR1-containing KATP channels. Here we report the serendipitous discovery in a high-throughput screen of a novel activator of Kir6.2/SUR1: VU0071063 [7-(4-(tert-butyl)benzyl)-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione]. The xanthine derivative rapidly and dose-dependently activates Kir6.2/SUR1 with a half-effective concentration (EC50) of approximately 7 μM, is more efficacious than diazoxide at low micromolar concentrations, directly activates the channel in excised membrane patches, and is selective for SUR1- over SUR2A-containing Kir6.1 or Kir6.2 channels, as well as Kir2.1, Kir2.2, Kir2.3, Kir3.1/3.2, and voltage-gated potassium channel 2.1. Finally, we show that VU0071063 activates native Kir6.2/SUR1 channels, thereby inhibiting glucose-stimulated calcium entry in isolated mouse pancreatic β cells. VU0071063 represents a novel tool/compound for investigating β-cell physiology, KATP channel gating, and a new chemical scaffold for developing improved activators with medicinal chemistry.
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Affiliation(s)
- Rene Raphemot
- Departments of Anesthesiology (R.R., D.R.S., S.B., J.S.D.), Pharmacology (R.R., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.) and Institutes of Chemical Biology (J.S.D.) and Global Health (J.S.D.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, University of Rochester Medical Center, Rochester, New York (A.P.W.); and Department of Cell Biology and Physiology (P.C., C.G.N.) and Center for the Investigation of Membrane Excitability Disorders (P.C., C.G.N.), Washington University School of Medicine in St. Louis, St. Louis, Missouri
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46
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Swale DR, Kharade SV, Denton JS. Cardiac and renal inward rectifier potassium channel pharmacology: emerging tools for integrative physiology and therapeutics. Curr Opin Pharmacol 2013; 15:7-15. [PMID: 24721648 DOI: 10.1016/j.coph.2013.11.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 11/05/2013] [Indexed: 01/01/2023]
Abstract
Inward rectifier potassium (Kir) channels play fundamental roles in cardiac and renal function and may represent unexploited drug targets for cardiovascular diseases. However, the limited pharmacology of Kir channels has slowed progress toward exploring their integrative physiology and therapeutic potential. Here, we review recent progress toward developing the small-molecule pharmacology for Kir2.x, Kir4.1, and Kir7.1 and discuss common mechanistic themes that may help guide future Kir channel-directed drug discovery efforts.
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Affiliation(s)
- Daniel R Swale
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Sujay V Kharade
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Jerod S Denton
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Institute for Global Health, Vanderbilt University Medical Center, Nashville, TN 37232, United States.
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47
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Tsikolia M, Bernier UR, Coy MR, Chalaire KC, Becnel JJ, Agramonte NM, Tabanca N, Wedge DE, Clark GG, Linthicum KJ, Swale DR, Bloomquist JR. Insecticidal, repellent and fungicidal properties of novel trifluoromethylphenyl amides. Pestic Biochem Physiol 2013; 107:138-47. [PMID: 25149248 DOI: 10.1016/j.pestbp.2013.06.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 06/07/2013] [Accepted: 06/08/2013] [Indexed: 05/16/2023]
Abstract
Twenty trifluoromethylphenyl amides were synthesized and evaluated as fungicides and as mosquito toxicants and repellents. Against Aedes aegypti larvae, N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-3,5-dinitrobenzamide (1e) was the most toxic compound (24 h LC50 1940 nM), while against adults N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-2,2,2-trifluoroacetamide (1c) was most active (24 h LD50 19.182 nM, 0.5 μL/insect). However, the 24 h LC50 and LD50 values of fipronil against Ae. aegypti larvae and adults were significantly lower: 13.55 nM and 0.787 × 10(-4) nM, respectively. Compound 1c was also active against Drosophila melanogaster adults with 24 h LC50 values of 5.6 and 4.9 μg/cm(2) for the Oregon-R and 1675 strains, respectively. Fipronil had LC50 values of 0.004 and 0.017 μg/cm(2) against the two strains of D. melanogaster, respectively. In repellency bioassays against female Ae. aegypti, 2,2,2-trifluoro-N-(2-(trifluoromethyl)phenyl)acetamide (4c) had the highest repellent potency with a minimum effective dosage (MED) of 0.039 μmol/cm(2) compared to DEET (MED of 0.091 μmol/cm(2)). Compound N-(2-(trifluoromethyl)phenyl)hexanamide (4a) had an MED of 0.091 μmol/cm(2) which was comparable to DEET. Compound 4c was the most potent fungicide against Phomopsis obscurans. Several trends were discerned between the structural configuration of these molecules and the effect of structural changes on toxicity and repellency. Para- or meta- trifluoromethylphenyl amides with an aromatic ring attached to the carbonyl carbon showed higher toxicity against Ae. aegypti larvae, than ortho- trifluoromethylphenyl amides. Ortho- trifluoromethylphenyl amides with trifluoromethyl or alkyl group attached to the carbonyl carbon produced higher repellent activity against female Ae. aegypti and Anopheles albimanus than meta- or para- trifluoromethylphenyl amides. The presence of 2,6-dichloro- substitution on the phenyl ring of the amide had an influence on larvicidal and repellent activity of para- trifluoromethylphenyl amides.
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Affiliation(s)
- Maia Tsikolia
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA.
| | - Ulrich R Bernier
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA
| | - Monique R Coy
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA
| | - Katelyn C Chalaire
- Navy Entomology Center of Excellence, PO Box 43, Bldg 937, Naval Air Station, Jacksonville, FL 32212-0043, USA
| | - James J Becnel
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA
| | - Natasha M Agramonte
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA
| | - Nurhayat Tabanca
- National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, The University of Mississippi, University, MS 38677, USA
| | - David E Wedge
- U.S. Department of Agriculture-Agricultural Research Service, Natural Products Utilization Research Unit, The University of Mississippi, University, MS 38677, USA
| | - Gary G Clark
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA
| | - Kenneth J Linthicum
- U.S. Department of Agriculture-Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32608, USA
| | - Daniel R Swale
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610-0009, USA
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610-0009, USA
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48
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Swale DR, Tong F, Temeyer KB, Li A, Lam PCH, Totrov MM, Carlier PR, Pérez de León AA, Bloomquist JR. Inhibitor profile of bis(n)-tacrines and N-methylcarbamates on acetylcholinesterase from Rhipicephalus (Boophilus) microplus and Phlebotomus papatasi. Pestic Biochem Physiol 2013; 106:10.1016/j.pestbp.2013.03.005. [PMID: 24187393 PMCID: PMC3811934 DOI: 10.1016/j.pestbp.2013.03.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The cattle tick, Rhipicephalus (Boophilus) microplus (Bm), and the sand fly, Phlebotomus papatasi (Pp), are disease vectors to cattle and humans, respectively. The purpose of this study was to characterize the inhibitor profile of acetylcholinesterases from Bm (BmAChE1) and Pp (PpAChE) compared to human and bovine AChE, in order to identify divergent pharmacology that might lead to selective inhibitors. Results indicate that BmAChE has low sensitivity (IC50 = 200 μM) toward tacrine, a monovalent catalytic site inhibitor with sub micromolar blocking potency in all previous species tested. Similarly, a series of bis(n)-tacrine dimer series, bivalent inhibitors and peripheral site AChE inhibitors possess poor potency toward BmAChE. Molecular homology models suggest the rBmAChE enzyme possesses a W384F orthologous substitution near the catalytic site, where the larger tryptophan side chain obstructs the access of larger ligands to the active site, but functional analysis of this mutation suggests it only partially explains the low sensitivity to tacrine. In addition, BmAChE1 and PpAChE have low nanomolar sensitivity to some experimental carbamate anticholinesterases originally designed for control of the malaria mosquito, Anopheles gambiae. One experimental compound, 2-((2-ethylbutyl)thio)phenyl methylcarbamate, possesses >300-fold selectivity for BmAChE1 and PpAChE over human AChE, and a mouse oral LD50 of >1500 mg/kg, thus providing an excellent new lead for vector control.
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Affiliation(s)
- Daniel R. Swale
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32611, USA
| | - Fan Tong
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32611, USA
| | - Kevin B. Temeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, United States Department of Agricultural-Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA
| | - Andrew Li
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, United States Department of Agricultural-Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA
| | - Polo C-H. Lam
- Molsoft LLC, 3366 North Torrey Pines Court, Suite 300, La Jolla, CA, 92037, USA
| | - Maxim M. Totrov
- Molsoft LLC, 3366 North Torrey Pines Court, Suite 300, La Jolla, CA, 92037, USA
| | - Paul R. Carlier
- Department of Chemistry, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Adalberto A. Pérez de León
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, United States Department of Agricultural-Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA
| | - Jeffrey R. Bloomquist
- Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32611, USA
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