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Pharmacological and Genetic Evidence for Gap Junctions as Potential New Insecticide Targets in the Yellow Fever Mosquito, Aedes aegypti.

Calkins TL, Piermarini PM - PLoS ONE (2015)

Bottom Line: We show that the injection of pharmacological inhibitors of gap junctions (i.e., carbenoxolone, meclofenamic acid, or mefloquine) into the hemolymph of adult female mosquitoes elicits dose-dependent toxic effects, with mefloquine showing the greatest potency.When added to the rearing water of 1st instar larvae, carbenoxolone and meclofenamic acid both elicit dose-dependent toxic effects, with meclofenamic acid showing the greatest potency.Injecting a double-stranded RNA cocktail against innexins into the hemolymph of adult female mosquitoes knock down whole-animal innexin mRNA expression and decreases survival of the mosquitoes.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, United States of America.

ABSTRACT
The yellow fever mosquito Aedes aegypti is an important vector of viral diseases that impact global health. Insecticides are typically used to manage mosquito populations, but the evolution of insecticide resistance is limiting their effectiveness. Thus, identifying new molecular and physiological targets in mosquitoes is needed to facilitate insecticide discovery and development. Here we test the hypothesis that gap junctions are valid molecular and physiological targets for new insecticides. Gap junctions are intercellular channels that mediate direct communication between neighboring cells and consist of evolutionarily distinct proteins in vertebrate (connexins) and invertebrate (innexins) animals. We show that the injection of pharmacological inhibitors of gap junctions (i.e., carbenoxolone, meclofenamic acid, or mefloquine) into the hemolymph of adult female mosquitoes elicits dose-dependent toxic effects, with mefloquine showing the greatest potency. In contrast, when applied topically to the cuticle, carbenoxolone was the only inhibitor to exhibit full efficacy. In vivo urine excretion assays demonstrate that both carbenoxolone and mefloquine inhibit the diuretic output of adult female mosquitoes, suggesting inhibition of excretory functions as part of their mechanism of action. When added to the rearing water of 1st instar larvae, carbenoxolone and meclofenamic acid both elicit dose-dependent toxic effects, with meclofenamic acid showing the greatest potency. Injecting a double-stranded RNA cocktail against innexins into the hemolymph of adult female mosquitoes knock down whole-animal innexin mRNA expression and decreases survival of the mosquitoes. Taken together these data indicate that gap junctions may provide novel molecular and physiological targets for the development of insecticides.

No MeSH data available.


Related in: MedlinePlus

Effects of gap junction inhibitors on the diuretic capacity of adult female A. aegypti mosquitoes.C = non-injected control mosquitoes. VL = volume loaded mosquitoes injected with 900 nl of HBS. VL + CBX = mosquitoes injected with 900 nl of HBS and 1.34 mM carbenoxolone. VL + MEF = mosquitoes injected with 900 nl of HBS and 0.5 mM mefloquine. VL + MFA = mosquitoes injected with 900 nl of HBS and 1.53 mM meclofenamic acid. Letters (A, B or C) indicate statistical differences as determined by a one-way ANOVA and Newman-Keuls post-test (P < 0.05). Values are mean volumes of urine excreted per mosquito after two hours ± SEM. n = 14 for VL, n = 14 for C, n = 8 for VL + CBX, n = 6 for VL + MEF, and n = 6 for VL + MFA.
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pone.0137084.g003: Effects of gap junction inhibitors on the diuretic capacity of adult female A. aegypti mosquitoes.C = non-injected control mosquitoes. VL = volume loaded mosquitoes injected with 900 nl of HBS. VL + CBX = mosquitoes injected with 900 nl of HBS and 1.34 mM carbenoxolone. VL + MEF = mosquitoes injected with 900 nl of HBS and 0.5 mM mefloquine. VL + MFA = mosquitoes injected with 900 nl of HBS and 1.53 mM meclofenamic acid. Letters (A, B or C) indicate statistical differences as determined by a one-way ANOVA and Newman-Keuls post-test (P < 0.05). Values are mean volumes of urine excreted per mosquito after two hours ± SEM. n = 14 for VL, n = 14 for C, n = 8 for VL + CBX, n = 6 for VL + MEF, and n = 6 for VL + MFA.

Mentions: To determine if the gap junction inhibitors disrupt the diuretic capacity of adult female mosquitoes, we volume loaded their hemolymph with a sub-lethal dose of each inhibitor. Fig 3 shows the mean volume excreted per female in 2 h after injection for each treatment, compared to the non-injected controls (C). Mosquitoes injected with a volume load (VL) and no inhibitor excreted on average 760 ± 16 nl (Fig 3). In contrast, those injected with a VL and 1.34 mM carbenoxolone (VL + CBX) excreted a significantly lower amount of urine (8.0 ± 8 nl) that is similar to non-injected control mosquitoes, which excrete 39 ± 8 nl (Fig 3). Mosquitoes injected with a VL and 0.5 mM mefloquine (VL + MEF) excrete 290 ± 93 nl, which was significantly lower than the amount excreted by the VL mosquitoes, but significantly higher than that excreted by the VL + CBX mosquitoes (Fig 3). Mosquitoes injected with a VL and 1.53 mM meclofenamic acid (VL + MFA) excrete 844 ± 14 nl, which was comparable to that of VL mosquitoes (Fig 3). Concentrations of meclofenamic acid higher than 1.53 mM were lethal to the mosquitoes before the end of the 2 h excretion assay (data not shown).


Pharmacological and Genetic Evidence for Gap Junctions as Potential New Insecticide Targets in the Yellow Fever Mosquito, Aedes aegypti.

Calkins TL, Piermarini PM - PLoS ONE (2015)

Effects of gap junction inhibitors on the diuretic capacity of adult female A. aegypti mosquitoes.C = non-injected control mosquitoes. VL = volume loaded mosquitoes injected with 900 nl of HBS. VL + CBX = mosquitoes injected with 900 nl of HBS and 1.34 mM carbenoxolone. VL + MEF = mosquitoes injected with 900 nl of HBS and 0.5 mM mefloquine. VL + MFA = mosquitoes injected with 900 nl of HBS and 1.53 mM meclofenamic acid. Letters (A, B or C) indicate statistical differences as determined by a one-way ANOVA and Newman-Keuls post-test (P < 0.05). Values are mean volumes of urine excreted per mosquito after two hours ± SEM. n = 14 for VL, n = 14 for C, n = 8 for VL + CBX, n = 6 for VL + MEF, and n = 6 for VL + MFA.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4556631&req=5

pone.0137084.g003: Effects of gap junction inhibitors on the diuretic capacity of adult female A. aegypti mosquitoes.C = non-injected control mosquitoes. VL = volume loaded mosquitoes injected with 900 nl of HBS. VL + CBX = mosquitoes injected with 900 nl of HBS and 1.34 mM carbenoxolone. VL + MEF = mosquitoes injected with 900 nl of HBS and 0.5 mM mefloquine. VL + MFA = mosquitoes injected with 900 nl of HBS and 1.53 mM meclofenamic acid. Letters (A, B or C) indicate statistical differences as determined by a one-way ANOVA and Newman-Keuls post-test (P < 0.05). Values are mean volumes of urine excreted per mosquito after two hours ± SEM. n = 14 for VL, n = 14 for C, n = 8 for VL + CBX, n = 6 for VL + MEF, and n = 6 for VL + MFA.
Mentions: To determine if the gap junction inhibitors disrupt the diuretic capacity of adult female mosquitoes, we volume loaded their hemolymph with a sub-lethal dose of each inhibitor. Fig 3 shows the mean volume excreted per female in 2 h after injection for each treatment, compared to the non-injected controls (C). Mosquitoes injected with a volume load (VL) and no inhibitor excreted on average 760 ± 16 nl (Fig 3). In contrast, those injected with a VL and 1.34 mM carbenoxolone (VL + CBX) excreted a significantly lower amount of urine (8.0 ± 8 nl) that is similar to non-injected control mosquitoes, which excrete 39 ± 8 nl (Fig 3). Mosquitoes injected with a VL and 0.5 mM mefloquine (VL + MEF) excrete 290 ± 93 nl, which was significantly lower than the amount excreted by the VL mosquitoes, but significantly higher than that excreted by the VL + CBX mosquitoes (Fig 3). Mosquitoes injected with a VL and 1.53 mM meclofenamic acid (VL + MFA) excrete 844 ± 14 nl, which was comparable to that of VL mosquitoes (Fig 3). Concentrations of meclofenamic acid higher than 1.53 mM were lethal to the mosquitoes before the end of the 2 h excretion assay (data not shown).

Bottom Line: We show that the injection of pharmacological inhibitors of gap junctions (i.e., carbenoxolone, meclofenamic acid, or mefloquine) into the hemolymph of adult female mosquitoes elicits dose-dependent toxic effects, with mefloquine showing the greatest potency.When added to the rearing water of 1st instar larvae, carbenoxolone and meclofenamic acid both elicit dose-dependent toxic effects, with meclofenamic acid showing the greatest potency.Injecting a double-stranded RNA cocktail against innexins into the hemolymph of adult female mosquitoes knock down whole-animal innexin mRNA expression and decreases survival of the mosquitoes.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, United States of America.

ABSTRACT
The yellow fever mosquito Aedes aegypti is an important vector of viral diseases that impact global health. Insecticides are typically used to manage mosquito populations, but the evolution of insecticide resistance is limiting their effectiveness. Thus, identifying new molecular and physiological targets in mosquitoes is needed to facilitate insecticide discovery and development. Here we test the hypothesis that gap junctions are valid molecular and physiological targets for new insecticides. Gap junctions are intercellular channels that mediate direct communication between neighboring cells and consist of evolutionarily distinct proteins in vertebrate (connexins) and invertebrate (innexins) animals. We show that the injection of pharmacological inhibitors of gap junctions (i.e., carbenoxolone, meclofenamic acid, or mefloquine) into the hemolymph of adult female mosquitoes elicits dose-dependent toxic effects, with mefloquine showing the greatest potency. In contrast, when applied topically to the cuticle, carbenoxolone was the only inhibitor to exhibit full efficacy. In vivo urine excretion assays demonstrate that both carbenoxolone and mefloquine inhibit the diuretic output of adult female mosquitoes, suggesting inhibition of excretory functions as part of their mechanism of action. When added to the rearing water of 1st instar larvae, carbenoxolone and meclofenamic acid both elicit dose-dependent toxic effects, with meclofenamic acid showing the greatest potency. Injecting a double-stranded RNA cocktail against innexins into the hemolymph of adult female mosquitoes knock down whole-animal innexin mRNA expression and decreases survival of the mosquitoes. Taken together these data indicate that gap junctions may provide novel molecular and physiological targets for the development of insecticides.

No MeSH data available.


Related in: MedlinePlus