Unravelling the potential of insects for medicinal purposes - A comprehensive review

Entomotherapy, the use of insects for medicinal purposes, has been practised for centuries in many countries around the world. More than 2100 edible insect species are eaten by humans, but little is known about the possibility of using these insects as a promising alternative to traditional pharmaceuticals for treating diseases. This review offers a fundamental understanding of the therapeutic applications of insects and how they might be used in medicine. In this review, 235 insect species from 15 orders are reported to be used as medicine. Hymenoptera contains the largest medicinal insect species, followed by Coleoptera, Orthoptera, Lepidoptera, and Blattodea. Scientists have examined and validated the potential uses of insects along with their products and by-products in treating various diseases, and records show that they are primarily used to treat digestive and skin disorders. Insects are known to be rich sources of bioactive compounds, explaining their therapeutic features such as anti-inflammatory, antimicrobial, antiviral, and so on. Challenges associated with the consumption of insects (entomophagy) and their therapeutic uses include regulation barriers and consumer acceptance. Moreover, the overexploitation of medicinal insects in their natural habitat has led to a population crisis, thus necessitating the investigation and development of their mass-rearing procedure. Lastly, this review suggests potential directions for developing insects used in medicine and offers advice for scientists interested in entomotherapy. In future, entomotherapy may become a sustainable and cost-effective solution for treating various ailments and has the potential to revolutionize modern medicine.

Unusual Lipid Components of Legionella gormanii Membranes

Legionella spp. cause Legionnaires’ disease with pneumonia as the predominant clinical symptom. L. gormanii is the second most prevalent causative agent of community-acquired pneumonia after L. pneumophila. The study aimed to characterize the lipidome of L. gormanii membranes and the importance of these analyses in bacterial chemotaxonomy. Lipidomic analyses based on ultra-high performance liquid chromatography-mass spectrometry allowed the detection of individual molecular species of a wide range of L. gormanii membrane lipids contained in the outer (OM) and inner membranes (IM). The lipid profile comprised glycerolipids (triglycerides, diglycerides), phospholipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, cardiolipin), and sphingolipids (ceramides, hexosylceramides). The most abundant lipid fraction in the IM and OM were phospholipids. The lipidomic analysis showed that two independent phosphatidylcholine (PC) synthesis pathways operating in L. gormanii: the PE-methylation (PmtA) pathway and the PC synthase (Pcs) pathway. Comparison of the molecular profile of PC species contained in the lipids of L. gormanii membranes cultured on the medium, with and without exogenous choline, showed quantitative differences in the PC pool. An unusual feature of the L. gormanii lipids was the presence of ceramides and hexosylceramides, which are typical components of eukaryotic cells and a very small group of bacteria. To the best of our knowledge, this is the first report of the occurrence of ceramides in Legionella bacteria.

Choline Supplementation Sensitizes Legionella dumoffii to Galleria mellonella Apolipophorin III

The growth of Legionella dumoffii can be inhibited by Galleria mellonella apolipophorin III (apoLp-III) which is an insect homologue of human apolipoprotein E., and choline-cultured L. dumoffii cells are considerably more susceptible to apoLp-III than bacteria grown without choline supplementation. In the present study, the interactions of apoLp-III with intact L. dumoffii cells cultured without and with exogenous choline were analyzed to explain the basis of this difference. Fluorescently labeled apoLp-III (FITC-apoLp-III) bound more efficiently to choline-grown L. dumoffii, as revealed by laser scanning confocal microscopy. The cell envelope of these bacteria was penetrated more deeply by FITC-apoLp-III, as demonstrated by fluorescence lifetime imaging microscopy analyses. The increased susceptibility of the choline-cultured L. dumoffii to apoLp-III was also accompanied by alterations in the cell surface topography and nanomechanical properties. A detailed analysis of the interaction of apoLp-III with components of the L. dumoffii cells was carried out using both purified lipopolysaccharide (LPS) and liposomes composed of L. dumoffii phospholipids and LPS. A single micelle of L. dumoffii LPS was formed from 12 to 29 monomeric LPS molecules and one L. dumoffii LPS micelle bound two molecules of apoLp-III. ApoLp-III exhibited the strongest interactions with liposomes with incorporated LPS formed of phospholipids isolated from bacteria cultured on exogenous choline. These results indicated that the differences in the phospholipid content in the cell membrane, especially PC, and LPS affected the interactions of apoLp-III with bacterial cells and suggested that these differences contributed to the increased susceptibility of the choline-cultured L. dumoffii to G. mellonella apoLp-III.

The Galleria mellonella larvae as an in vivo model for evaluation of Shigella virulence

Shigella spp. causing bacterial diarrhea and dysentery are human enteroinvasive bacterial pathogens that are orally transmitted through contaminated food and water and cause bacillary dysentery. Although natural Shigella infections are restricted to humans and primates, several smaller animal models are used to analyze individual steps in pathogenesis. No animal model fully duplicates the human response and sustaining the models requires expensive animals, costly maintenance of animal facilities, veterinary services and approved animal protocols. This study proposes the development of the caterpillar larvae of Galleria mellonella as a simple, inexpensive, informative, and rapid in-vivo model for evaluating virulence and the interaction of Shigella with cells of the insect innate immunity. Virulent Shigella injected through the forelegs causes larvae death. The mortality rates were dependent on the Shigella strain, the infectious dose, and the presence of the virulence plasmid. Wild-type S. flexneri 2a, persisted and replicated within the larvae, resulting in haemocyte cell death, whereas plasmid-cured mutants were rapidly cleared. Histology of the infected larvae in conjunction with fluorescence, immunofluorescence, and transmission electron microscopy indicate that S. flexneri reside within a vacuole of the insect haemocytes that ultrastructurally resembles vacuoles described in studies with mouse and human macrophage cell lines. Some of these bacteria-laden vacuoles had double-membranes characteristic of autophagosomes. These results suggest that G. mellonella larvae can be used as an easy-to-use animal model to understand Shigella pathogenesis that requires none of the time and labor-consuming procedures typical of other systems.

The lipid composition of Legionella dumoffii membrane modulates the interaction with Galleria mellonella apolipophorin III

Apolipophorin III (apoLp-III), an insect homologue of human apolipoprotein E (apoE), is a widely used model protein in studies on protein-lipid interactions, and anti-Legionella activity of Galleria mellonella apoLp-III has been documented. Interestingly, exogenous choline-cultured Legionella dumoffii cells are considerably more susceptible to apoLp-III than non-supplemented bacteria. In order to explain these differences, we performed, for the first time, a detailed analysis of L. dumoffii lipids and a comparative lipidomic analysis of membranes of bacteria grown without and in the presence of exogenous choline. (31)P NMR analysis of L. dumoffii phospholipids (PLs) revealed a considerable increase in the phosphatidylcholine (PC) content in bacteria cultured on choline medium and a decrease in the phosphatidylethanolamine (PE) content in approximately the same range. The interactions of G. mellonella apoLp-III with lipid bilayer membranes prepared from PLs extracted from non- and choline-supplemented L. dumoffii cells were examined in detail by means of attenuated total reflection- and linear dichroism-Fourier transform infrared spectroscopy. Furthermore, the kinetics of apoLp-III binding to liposomes formed from L. dumoffii PLs was analysed by fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy using fluorescently labelled G. mellonella apoLp-III. Our results indicated enhanced binding of apoLp-III to and deeper penetration into lipid membranes formed from PLs extracted from the choline-supplemented bacteria, i.e. characterized by an increased PC/PE ratio. This could explain, at least in part, the higher susceptibility of choline-cultured L. dumoffii to G. mellonella apoLp-III.

Legionella pneumophila: The Paradox of a Highly Sensitive Opportunistic Waterborne Pathogen Able to Persist in the Environment

Legionella pneumophila, the major causative agent of Legionnaires’ disease, is found in freshwater environments in close association with free-living amoebae and multispecies biofilms, leading to persistence, spread, biocide resistance, and elevated virulence of the bacterium. Indeed, legionellosis outbreaks are mainly due to the ability of this bacterium to colonize and persist in water facilities, despite harsh physical and chemical treatments. However, these treatments are not totally efficient and, after a lag period, L. pneumophila may be able to quickly re-colonize these systems. Several natural compounds (biosurfactants, antimicrobial peptides…) with anti-Legionella properties have recently been described in the literature, highlighting their specific activities against this pathogen. In this review, we first consider this hallmark of Legionella to resist killing, in regard to its biofilm or host-associated life style. Then, we focus more accurately on natural anti-Legionella molecules described so far, which could provide new eco-friendly and alternative ways to struggle against this important pathogen in plumbing.

Analysis of cell surface alterations in Legionella pneumophila cells treated with human apolipoprotein E

Binding of human apolipoprotein E (apoE) to Legionella pneumophila lipopolysaccharide was analysed at the molecular level by Fourier-transform infrared spectroscopy, thereby providing biophysical evidence for apoE-L. pneumophila lipopolysaccharide interaction. Atomic force microscopy imaging of apoE-exposed L. pneumophila cells revealed alterations in the bacterial cell surface topography and nanomechanical properties in comparison with control bacteria. The changes induced by apoE binding to lipopolysaccharide on the surface of L. pneumophila cells may participate in: (1) impeding the penetration of host cells by the bacteria; (2) suppression of pathogen intracellular growth and eventually; and (3) inhibition of the development of infection.