Biochimie et Toxicologie des Substances Bioactives

Ants (Formicidae) represent a taxonomically diverse group of hymenopterans with over 13,000 extant species, the majority of which inject or spray secretions from a venom gland. The evolutionary success of ants is mostly due to their unique eusociality that has permitted them to develop complex collaborative strategies, partly involving their venom secretions, to defend their nest against predators, microbial pathogens, ant competitors, and to hunt prey. Activities of ant venom include paralytic, cytolytic, haemolytic, allergenic, pro-inflammatory, insecticidal, antimicrobial, and pain-producing pharmacologic activities, while non-toxic functions include roles in chemical communication involving trail and sex pheromones, deterrents, and aggregators. While these diverse activities in ant venoms have until now been largely understudied due to the small venom yield from ants, modern analytical and venomic techniques are beginning to reveal the diversity of toxin structure and function. As such, ant venoms are distinct from other venomous animals, not only rich in linear, dimeric and disulfide-bonded peptides and bioactive proteins, but also other volatile and non-volatile compounds such as alkaloids and hydrocarbons. The present review details the unique structures and pharmacologies of known ant venom proteinaceous and alkaloidal toxins and their potential as a source of novel bioinsecticides and therapeutic agents.

Trikafta, currently the leading therapeutic in cystic fibrosis (CF), has demonstrated a real clinical benefit. This treatment is the triple combination therapy of two folding correctors elexacaftor/tezacaftor (VX445/VX661) plus the gating potentiator ivacaftor (VX770). In this study, our aim was to compare the properties of F508del-CFTR in cells treated with either lumacaftor (VX809), tezacaftor, elexacaftor, elexacaftor/tezacaftor with or without ivacaftor. We studied F508del-CFTR function, maturation and membrane localisation by Ussing chamber and whole-cell patch-clamp recordings, Western blot and immunolocalisation experiments. With human primary airway epithelial cells and the cell lines CFBE and BHK expressing F508del, we found that, whereas the combination elexacaftor/tezacaftor/ivacaftor was efficient in rescuing F508del-CFTR abnormal maturation, apical membrane location and function, the presence of ivacaftor limits these effects. The basal F508del-CFTR short-circuit current was significantly increased by elexacaftor/tezacaftor/ivacaftor and elexacaftor/tezacaftor compared to other correctors and nontreated cells, an effect dependent on ivacaftor and cAMP. These results suggest that the level of the basal F508del-CFTR current might be a marker for correction efficacy in CF cells. When cells were treated with ivacaftor combined to any correctors, the F508del-CFTR current was unresponsive to the subsequently acute addition of ivacaftor, unlike the CFTR (cystic fibrosis transmembrane conductance regulator) potentiators genistein and Cact-A1 which increased elexacaftor/tezacaftor/ivacaftor and elexacaftor/tezacaftor-corrected F508del-CFTR currents. These findings show that ivacaftor reduces the correction efficacy of Trikafta. Thus, combining elexacaftor/tezacaftor with a different potentiator might improve the therapeutic efficacy for treating CF patients.

Using an integrated transcriptomic and proteomic approach, we characterized the venom peptidome of the European red ant, Manica rubida . We identified 13 “myrmicitoxins” that share sequence similarities with previously identified ant venom peptides, one of them being identified as an EGF-like toxin likely resulting from a threonine residue modified by O- fucosylation. Furthermore, we conducted insecticidal assays of reversed-phase HPLC venom fractions on the blowfly Lucilia caesar, permitting us to identify six myrmicitoxins (i.e., U 3 -, U 10 -, U 13 -, U 20 -MYRTX-Mri1a, U 10 -MYRTX-Mri1b, and U 10 -MYRTX-Mri1c) with an insecticidal activity. Chemically synthesized U 10 -MYRTX-Mri1a, -Mri1b, -Mri1c, and U 20 -MYRTX-Mri1a irreversibly paralyzed blowflies at the highest doses tested (30–125 nmol·g –1 ). U 13 -MYRTX-Mri1a, the most potent neurotoxic peptide at 1 h, had reversible effects after 24 h (150 nmol·g –1 ). Finally, U 3 -MYRTX-Mri1a has no insecticidal activity, even at up to 55 nmol·g –1 . Thus, M. rubida employs a paralytic venom rich in linear insecticidal peptides, which likely act by disrupting cell membranes.

The venom peptide bicarinalin, previously isolated from the ant Tetramorium bicarinatum, is an antimicrobial agent with a broad spectrum of activity. In this study, we investigate the potential of bicarinalin as a novel agent against Helicobacter pylori, which causes several gastric diseases. First, the effects of synthetic bicarinalin have been tested against Helicobacter pylori: one ATCC strain, and forty-four isolated from stomach ulcer biopsies of Peruvian patients. Then the cytoxicity of bicarinalin on human gastric cells and murine peritoneal macrophages was measured using XTT and MTT assays, respectively. Finally, the preventive effect of bicarinalin was evaluated by scanning electron microscopy using an adherence assay of H. pylori on human gastric cells treated with bicarinalin. This peptide has a potent antibacterial activity at the same magnitude as four antibiotics currently used in therapies against H. pylori. Bicarinalin also inhibited adherence of H. pylori to gastric cells with an IC50 of 0.12 μg·mL−1 and had low toxicity for human cells. Scanning electron microscopy confirmed that bicarinalin can significantly decrease the density of H. pylori on gastric cells. We conclude that Bicarinalin is a promising compound for the development of a novel and effective anti-H. pylori agent for both curative and preventive use.

Ants are among the most abundant terrestrial invertebrate predators on Earth. To overwhelm their prey, they employ several remarkable behavioral, physiological, and biochemical innovations, including an effective paralytic venom. Ant venoms are thus cocktails of toxins finely tuned to disrupt the physiological systems of insect prey. They have received little attention yet hold great promise for the discovery of novel insecticidal molecules. To identify insect-neurotoxins from ant venoms, we screened the paralytic activity on blowflies of nine synthetic peptides previously characterized in the venom of Tetramorium bicarinatum. We selected peptide U11, a 34-amino acid peptide, for further insecticidal, structural, and pharmacological experiments. Insecticidal assays revealed that U11 is one of the most paralytic peptides ever reported from ant venoms against blowflies and is also capable of paralyzing honeybees. An NMR spectroscopy of U11 uncovered a unique scaffold, featuring a compact triangular ring helix structure stabilized by a single disulfide bond. Pharmacological assays using Drosophila S2 cells demonstrated that U11 is not cytotoxic, but suggest that it may modulate potassium conductance, which structural data seem to corroborate and will be confirmed in a future extended pharmacological investigation. The results described in this paper demonstrate that ant venom is a promising reservoir for the discovery of neuroactive insecticidal peptides.

Hymenopterans represent one of the most abundant groups of venomous organisms but remain little explored due to the difficult access to their venom. The development of proteo-transcriptomic allowed us to explore diversity of their toxins offering interesting perspectives to identify new biological active peptides. This study focuses on U 9 function, a linear, amphiphilic and polycationic peptide isolated from ant Tetramorium bicarinatum venom. It shares physicochemical properties with M-Tb1a, exhibiting cytotoxic effects through membrane permeabilization. In the present study, we conducted a comparative functional investigation of U 9 and M-Tb1a and explored the mechanisms underlying their cytotoxicity against insect cells. After showing that both peptides induced the formation of pores in cell membrane, we demonstrated that U 9 induced mitochondrial damage and, at high concentrations, localized into cells and induced caspase activation. This functional investigation highlighted an original mechanism of U 9 questioning on potential valorization and endogen activity in T . bicarinatum venom.

Modern home‐range estimation typically relies on data derived from expensive radio‐ or GPS‐tracking. Although trapping represents a low‐cost alternative to telemetry, evaluation of the performance of home‐range estimators on trap‐derived data is lacking. Using simulated data, we evaluated three variables reflecting the key trade‐offs ecologists face when designing a trapping study: 1) the number of observations obtained per individual, 2) the trap density and 3) the proportion of the home range falling inside the trapping area. We compared the performance of five home‐range estimators (MCP: Minimum Convex Polygon, LoCoH: Local Convex Hull, KDE: Kernel Density Estimation, AKDE: Autocorrelated Kernel Density Estimation, BicubIt: Bicubic Interpolation). We further explored the potential benefits of combining these estimators with asymptotic models, which leverage the saturating behavior of changes in the estimated home‐range area as the number of observations increases to improve accuracy, as well as different data‐ordering procedures. We then quantified the bias in home‐range size under the different scenarios investigated. The number of observations and the proportion of the home range within the trapping grid were the most important predictors of the accuracy and the precision of home‐range estimates. The use of asymptotic models helped to obtain accurate estimates at smaller sample sizes, while distance ordering improved the precision and asymptotic consistency of estimates. While AKDE was the best performing estimator under most conditions evaluated, bicubic interpolation was a viable alternative under common real‐world conditions of low trap density and area covered. A case study using empirical data from white‐tailed deer in Florida and another from jaguars in Belize demonstrated support for the findings of our simulation results. Although researchers with trap data often overlook home‐range estimation, our results indicate that these data have the capacity to yield accurate estimates of home‐range size. Trapping data can, therefore, lower the economic costs of home‐range analysis, potentially enlarging the span of species, researchers and questions studied in ecology and conservation.

If you decide to make a list of the stinging insects to most carefully avoid on Earth, The Sting of the Wild is the perfect guide. This book is an entertaining tale of Justin Schmidt's life long research that will incontestably spark the interest of all entomologists. The book provides interesting ecological and behavioral information on a broad array of stinging insects (that is, wasps, hornets, bees, and ants) examined in an evolutionary context. Why do some hymenoptera venoms hurt and some others do not? Why is the bullet ant considered to have the most painful sting among insects? And why is the venom of the Maricopa harvester ant the most toxic for vertebrates? Through the author's own experience, the book discusses the relationship between hymenoptera and vertebrates, particularly humans. Schmidt explains how the evolution of a sting as well as pain-inducing venom has been critical to the rise of sociality among hymenoptera. Justin Schmidt is an American entomologist based at the University of Arizona who is interested in venom biochemistry and the pain induced by insect stings. He pioneered the study of hymenoptera venoms with the first descriptions of their composition and physiological effects, as well as a description of some venom toxins. He is also famous in the scientific community for having created the Schmidt sting pain index, in which various insects are ranked according to the pain induced by their sting. The pain index is based on his personal experience with insect stings. Throughout his numerous travels and field studies, Justin Schmidt has been stung, more or less deliberately, more than 1,000 times. Along with a list of species, their geographical distribution, and the pain level related to their stings, Schmidt's pain index provides an accurate, florid, and imaginative description of the pain caused by each species. Species are ranked from 0 to 4: painless insect stings are rated at 0, while the most painful top the scale at 4. Schmidt's curious field of study and unusual methods led him to be awarded an Ig Nobel Prize in 2015 in honor of his improbable research. The Sting of the Wild is part biography, part scientific book, in which the author shares his personal experience and expertise on insect venoms with readers. Although the book is sometimes a bit repetitive, it is highly readable and filled with fascinating anecdotes. Readers travel all around the world with Justin Schmidt, from the Costa Rican rainforest to the Arizonian desert, to encounter the creatures that most people usually attempt to avoid. The book is divided into eleven chapters. The first five chapters are introductory, with general statements on insects, stinger anatomy, evolution, and pain. The chapters that follow focus on several conspicuous and interesting stinging species, including as honey bees, the bullet ant, and yellow jackets, and contain valuable information and amusing stories. Throughout these chapters, we learn how the author encountered each species, the origin of the species’ names, the astonishing life history of these creatures, a description of the pain caused by their stings, and their ecological relevance. Even though very little is known about the composition of insect venoms, Schmidt provides some details on their chemical components. For instance, Schmidt describes the sting of the bullet ant as “pure, intense, brilliant pain. Like walking over flaming charcoal with a 3-inch nail embedded in your heel.” He explains how he has injected under his own skin a “tiny amount of synthetic poneratoxin” in order to check if this toxin was the pain-inducing toxin of the venom. We can also appreciate the beauty and variety of the insects that are mentioned in the book through several photographs presented in a central section. The book concludes with the complete Schmidt pain index for 83 species of stinging insects and the list of references used in the book. You don't need to have been stung by a lot of ants or any other insects to appreciate this book. The Sting of the Wild sheds light on the mysteries of stinging insects in a delightful and humorous narration. I recommend the book to every entomologist, ecologist, and naturalist interested in exploring the impressive world of Hymenoptera.

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The oil sands area of northern Alberta has river sediments that contain natural bitumen. Eggs and fish in these rivers may be exposed to bitumen-related chemicals early in life. This paper assesses a short embryo-larval fish exposure to oil sands sediment and follows the fish behaviour as they mature in clean water and examines their breeding success as adults (5 months afterwards). The three different oil sands river sediments tested were: a sediment collected outside of the bitumen deposit (tested at 3 g/L, Reference sediment from upstream Steepbank River site), and two sediments collected within the deposit (each tested at low (1 g/L) and high (3 g/L) concentrations). The sediments within the bitumen deposit were from the Ells and Steepbank (Stp) Rivers, and both contained significant total PAHs (>170 ng/g wet weight sediment) and alkylated PAHs (>4480 ng/g). Fish were exposed to these sediments for 21 days (as eggs and larval fish), and then transferred permanently to clean water to mature and breed. There was a significant decrease in the number of egg clutches produced by fish exposed early in life to Stp downstream high sediment (compared to Reference sediment). There was also a decrease in overall cumulative egg production, with fish from Stp downstream high sediment producing just over 1000 eggs in total while fish exposed to Ref sediment produced nearly 6900 eggs. The fish with reduced egg production were also less social than expected as they matured, and they had a lower % of early vitellogenic eggs in their ovaries. Overall, the exposure shows that a single, brief exposure during early life stages to natural bitumen can affect fish in adulthood. Naturally occurring bitumen-derived PAHs can reduce fish reproductive output by complex mechanisms, measurable as lower ovary maturity and changes in social behaviour.

Animal venoms are natural libraries of bioactive compounds, called toxins, which have been finetuned through the course of evolution. However, numerous venomous organisms are still neglected, especially venomous insects. Several studies of ant venoms revealed that they were peptide-rich. Furthermore, the characterization of the ant Tetramorium bicarinatum venom peptidome revealed that, despite the diversity of mature peptides, they belonged to 3 superfamilies of precursors, some of which have already been described in other aculeate hymenoptera. This study also observed that genes encoding some of them were expressed outside the venom apparatus. These results raise questions about the mechanisms involved in the diversification of peptide toxins from ant venoms, as well as their role apart from the venomous function. To address these issues, the first part of this thesis work consisted in the characterization via proteotranscriptomics approaches of 7 venoms from ants belonging to the different phylogenetic tribes of the Myrmicinae subfamily, and of the venom of one species. belonging to a close subfamily, the Pseudomyrmecinae. A total of 100 peptide toxins with various structures were thus identified and classified into 8 precursor superfamilies. The second part explored the link between peptide toxins of T. bicarinatum venom and its innate immunity via molecular and cellular biology methods. The presence of transcripts encoding certain peptides have been verified in organs which are involved in innate immunity of insects (i.e. fat bodies, digestive tracts). The expression of the genes encoding them has also been evaluated following a bacterial infection. It has thus been shown that the transcripts encoding the selected venom peptides are present in the organs tested, and that some are produced in fat bodies in response to a bacterial infection. These results confirm the existence of a link between the venom peptides and the innate immunity of the ant T. bicarinatum, although further studies are needed

Le bassin versant de la Seine peut etre considere comme representatif des bassins hydrographiques fortement impactes par l'activite humaine et a ce titre presente une forte pression de pollution. La pollution chimique constitue une menace supplementaire pour des ecosystemes aquatiques deja tres fragiles tels que les estuaires et les zones marines cotieres. Peu d'etudes se sont concentrees sur la contamination et l'impact des microplastiques (MP, taille < 5 mm) dans les ecosystemes estuariens et aucune a ce jour en estuaire de Seine. Le projet Plastic-Seine (GIP Seine-Aval et CPIER Vallee de Seine) vise d’une part a quantifier la presence et le flux de MP dans l'estuaire de la Seine et d’autre part a evaluer leur devenir et leur impact sur differentes especes du reseau trophique. Plusieurs campagnes de terrain ont ete menees depuis mars 2017 sur le continuum eau douce-eau salee a differentes saisons pour echantillonner les eaux de surface, les sediments et sept especes du reseau trophique (poissons, crustaces, mollusques, annelides) representatives de l'ecosysteme estuarienne de la Seine. Les premiers resultats indiquent une contamination moderee (1,8-5,1 fragments/m3) mais generalisee des differents compartiments abiotiques et biotiques par des MP comprenant principalement des fibres et des fragments. Des MP ont ete identifies dans toutes les especes analysees, quel que soit le site ou la saison de prelevement. Des expositions a des MP environnementaux en conditions controlees de laboratoire ont demontre l’ingestion mais aussi l’egestion tres rapide de ces MP par les annelides et la sole commune (les analyses sont en cours sur les copepodes). Des premiers effets significatifs des MP sur la survie et la reproduction du copepode E. affinis et sur le comportement des soles ont ete observes. Ce projet devrait fournir d’ici 2020 une premiere evaluation de la distribution et du flux de microplastiques dans l'estuaire de la Seine et de la faune aquatique associee.

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