The Repellent DEET Potentiates Carbamate Effects via Insect Muscarinic Receptor Interactions: An Alternative Strategy to Control Insect Vector-Borne Diseases

Abstract

Insect vector-borne diseases remain one of the principal causes of human mortality. In addition to conventional measures of insect control, repellents continue to be the mainstay for personal protection. Because of the increasing pyrethroid-resistant mosquito populations, alternative strategies to reconstitute pyrethroid repellency and knock-down effects have been proposed by mixing the repellent DEET (N,N-Diethyl-3-methylbenzamide) with non-pyrethroid insecticide to better control resistant insect vector-borne diseases. By using electrophysiological, biochemichal, in vivo toxicological techniques together with calcium imaging, binding studies and in silico docking, we have shown that DEET, at low concentrations, interacts with high affinity with insect M1/M3 mAChR allosteric site potentiating agonist effects on mAChRs coupled to phospholipase C second messenger pathway. This increases the anticholinesterase activity of the carbamate propoxur through calcium-dependent regulation of acetylcholinesterase. At high concentrations, DEET interacts with low affinity on distinct M1/M3 mAChR site, counteracting the potentiation. Similar dose-dependent dual effects of DEET have also been observed at synaptic mAChR level. Additionally, binding and in silico docking studies performed on human M1 and M3 mAChR subtypes indicate that DEET only displays a low affinity antagonist profile on these M1/M3 mAChRs. These results reveal a selective high affinity positive allosteric site for DEET in insect mAChRs. Finally, bioassays conducted on Aedes aegypti confirm the synergistic interaction between DEET and propoxur observed in vitro, resulting in a higher mortality of mosquitoes. Our findings reveal an unusual allosterically potentiating action of the repellent DEET, which involves a selective site in insect. These results open exciting research areas in public health particularly in the control of the pyrethroid-resistant insect-vector borne diseases. Mixing low doses of DEET and a non-pyrethroid insecticide will lead to improvement in the efficiency treatments thus reducing both the concentration of active ingredients and side effects for non-target organisms. The discovery of this insect specific site may pave the way for the development of new strategies essential in the management of chemical use against resistant mosquitoes.

Olfactory Mechanisms for Discovery of Odorants to Reduce Insect-Host Contact

“…These two attributes make it one of the most commonly used insect repellents in the developed world. However DEET has also been shown to dissolve nylons and plastics, blocks human acetylcholinesterase, activates human M3 muscarinic GPCR causing anti-angiogenesis, inhibits mammalian TRPM8, and inhibits mammalian CNGA2 channels, the health consequences of none of which are well understood (Abd-Ella 2015; Corbel 2009; Ditzen 2008; Legeay 2016; Swale 2015). The notion that identification of the mechanisms of action of DEET could help in the development of improved broad-spectrum repellents has resulted in much recent research in this area (Ray 2015).…”

The insect repellent N,N-diethyl-m-toluamide (DEET) induces angiogenesis via allosteric modulation of the M3 muscarinic receptor in endothelial cells

“…Other works by Kruse et al 32. on the M2 receptor and the simulation performed by Abd-Ella et al 49. on M1/M3 receptors did support the existence of an allosteric site in human M3 receptor.…”

“…Potential mechanisms are inhibition of acetylcholinesterase (AChE)8, modulation of muscarinic receptors49 or the well-conserved ionotropic receptor Ir40a, odorant receptors (OR) and gustatory receptors (GR)75051525354. Among these targets, it has been reported that some inhibitors of human AChE, like donepezil, rivastigmine or galantamine have pro-angiogenic properties in in vitro HUVEC cultured on ECMgel like in chick chorioallantoic membrane and/or in an ischemic hind limb model1455.…”

“…on M1/M3 receptors did support the existence of an allosteric site in human M3 receptor. At low concentration (10 −8  M), DEET interacts with high affinity with M1/M3 mAChR allosteric sites, whereas at high concentration (>10 −6  M), DEET interacts with a very low affinity49.…”

Virus and calcium: an unexpected tandem to optimize insecticide efficacy

“…To circumvent the problems raised above, the strategy we propose in this review is based on different previous complementary results reporting that (i) insect target sites are strongly regulated by calcium-dependent signalling pathways, (ii) manipulating intracellular regulatory mechanisms of insecticide target sites can have important consequences for the sensitivity of insects towards insecticides, and (iii) insect virus entry into the host cells can produce relatively fast intracellular calcium concentration rise (Thany et al, 2007;Lapied et al, 2009;Lavialle-Defaix et al, 2010;Licznar et al, 2014;List et al, 2014;Abd-Ella et al, 2015). In this case, the insect virus is not used as a bioinsecticide (i.e.…”