Maggot excretion products from the blowfly Lucilia sericata contain contact phase/intrinsic pathway-like proteases with procoagulant functions

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.

Análisis comparativo de la actividad antimicrobiana de secreciones y excreciones larvales de Calliphora vicina y Sarconesiopsis magellanica (Diptera: Calliphoridae)

Introducción.

La creciente resistencia bacteriana a los antibióticos representa una amenaza mundial de salud pública. Las excreciones y secreciones larvarias derivadas de moscas necrófagas de la familia Calliphoridae podrían configurar una fuente promisoria para contrarrestar sus efectos.

Objetivo.

Comparar la actividad antimicrobiana de las excreciones y secreciones larvarias nativas, y de las mayores y menores de 10 kDa de Calliphora vicina y Sarconesiopsis magellanica (Diptera: Calliphoridae).

Materiales y métodos.

El bioensayo se hizo a partir de la técnica de turbidimetría y en el caso de las excreciones y secreciones menores de 10 kDa se determinó la concentración inhibitoria mínima (CIM).

Resultados.

Las excreciones y secreciones nativas y las menores de 10 kDa de C. vicina y S. magellanica, evidenciaron una potente actividad antibacteriana contra tres cepas de Staphylococcus aureus y cuatro bacterias Gram negativas, siendo las menores de 10 kDa más efectivas que las nativas en las dos especies de moscas evaluadas. Además, las menores de 10 kDa presentaron la misma efectividad, aunque en las pruebas de CIM se observó que las de S. magellanica fueron más potentes en todas las bacterias evaluadas, excepto contra la cepa de S. aureus ATCC 25923. Las mayores de 10 kDa no inhibieron el crecimiento bacteriano.

Conclusión.

Los resultados validaron, en general, que estas sustancias son fuente importante para el aislamiento y la caracterización de agentes antimicrobianos.

The effect of Lucilia sericata larval excretion/secretion (ES) products on cellular responses in wound healing

Chronic wounds are still regarded as a serious public health concern, which are on the increase mainly due to the changes in life styles and aging of the human population. There are different types of chronic wounds, each of which requires slightly different treatment strategies. Nevertheless, wound bed preparation is included in treatment of all types of chronic wounds and involves tissue debridement, inflammation, and infection control, as well as moisture balance and epithelial edge advancement. Maggot therapy (MT) is a form of biological debridement which involves the application of live medical grade Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) larvae. Whereas it was initially thought to act mainly through debridement, today MT is known to influence all four overlapping physiological phases of wound repair: homeostasis, inflammation, proliferation, and remodelling/maturing. During MT, medical-grade larvae are applied either freely or enclosed in tea-bag like devices (biobag) inside the wounds, which suggests that larva excretion/secretion (ES) products can facilitate the healing processes directly without the need of direct contact with the larvae. This review summarizes the relevant literature on ES-mediated effects on the cellular responses involved in wound healing.

Pharmacological Properties of the Medical Maggot: A Novel Therapy Overview

In the last decade, maggot has been hailed as the miraculous “medicinal maggot” for its diverse properties, including antimicrobial, antibiofilm, anti-inflammatory, and wound healing activities. The fact that maggots show so many beneficial properties has increased the interest in these tiny larvae dramatically. Whilst there is relatively abundant clinical evidence to demonstrate the success of maggots as debridement agents, not so much emphasis has been placed on the basic science evidence, which was a combination of physical and biochemical actions. This review differs from those earlier works in that it is undertaken to provide an update of the latest scientific basis published on maggot, particularly active ingredients within maggot excretions/secretions (ES). Further investigations should focus on the isolation, identification, recombination, transgenosis, and mass production of the beneficial molecules within maggots.

Urate Oxidase produced by Lucilia sericata medical maggots is localized in Malpighian tubes and facilitates allantoin production

Lucilia sericata maggots are the only species currently approved for maggot debridement therapy (MDT), an alternative treatment for chronic and recalcitrant wounds. Maggots promote wound debridement, disinfection and healing by producing a complex mixture of proteins, peptides and low-molecular-weight compounds in their secretions and excretions, but the individual components are not well characterized at the molecular level. Here we investigated the purine catabolism pathway in L. sericata, focusing on the production of allantoin by Urate Oxidase (UO), which is thought to promote wound healing. We produced recombinant L. sericata UO in Escherichia coli, and characterized the properties of the pure enzyme in terms of the optimum pH (7-10) and temperature (20-25 °C), its stability, sensitivity to inhibition and ion dependency. We used quantitative RT-PCR and RNA in situ hybridization to monitor the expression of the UO gene, and we used a guinea pig anti-UO antibody to detect the native enzyme by western blot and by florescence immunohistochemistry in larval tissues. We found that L. sericata UO is exclusively present in the larval excretion organ (the Malpighian tubes) and is freely available in the cytoplasm rather than restricted to a specific subcellular compartment. Allantoin is a final product of L. sericata purine catabolism. It is produced by UO in the Malpighian tubes to remove uric acid from the hemolymph and is consequently excreted via the hindgut. Our findings confirm the hypothesis that both actively secreted molecules and excretion products contribute to the beneficial effects of MDT.

Next Generation Sequencing Identifies Five Major Classes of Potentially Therapeutic Enzymes Secreted by Lucilia sericata Medical Maggots

Lucilia sericata larvae are used as an alternative treatment for recalcitrant and chronic wounds. Their excretions/secretions contain molecules that facilitate tissue debridement, disinfect, or accelerate wound healing and have therefore been recognized as a potential source of novel therapeutic compounds. Among the substances present in excretions/secretions various peptidase activities promoting the wound healing processes have been detected but the peptidases responsible for these activities remain mostly unidentified. To explore these enzymes we applied next generation sequencing to analyze the transcriptomes of different maggot tissues (salivary glands, gut, and crop) associated with the production of excretions/secretions and/or with digestion as well as the rest of the larval body. As a result we obtained more than 123.8 million paired-end reads, which were assembled de novo using Trinity and Oases assemblers, yielding 41,421 contigs with an N50 contig length of 2.22 kb and a total length of 67.79 Mb. BLASTp analysis against the MEROPS database identified 1729 contigs in 577 clusters encoding five peptidase classes (serine, cysteine, aspartic, threonine, and metallopeptidases), which were assigned to 26 clans, 48 families, and 185 peptidase species. The individual enzymes were differentially expressed among maggot tissues and included peptidase activities related to the therapeutic effects of maggot excretions/secretions.

A Jonah-like chymotrypsin from the therapeutic maggot Lucilia sericata plays a role in wound debridement and coagulation

Lucilia sericata larvae are used in maggot debridement therapy, a traditional wound healing approach that has recently been approved for the treatment of chronic wounds. Maggot excretion products (MEP) contain many different proteases that promote disinfection, debridement and the acceleration of wound healing, e.g. by activating the host contact phase/intrinsic pathway of coagulation. In order to characterise relevant procoagulant proteases, we analysed MEP and identified a chymotrypsin-like serine protease with similarities to Jonah proteases from Drosophila melanogaster and a chymotrypsin from Lucilia cuprina. A recombinant form of the L. sericata Jonah chymotrypsin was produced in Escherichia coli. The activated enzyme (Jonahm) had a pH optimum of 8.0 and a temperature optimum of 37 °C, based on the cleavage of the chromogenic peptide s-7388 and casein. Jonahm reduced the clotting time of human plasma even in the absence of the endogenous protease kallikrein, factor XI or factor XII and digested the extracellular matrix proteins fibronectin, laminin and collagen IV, suggesting a potential mechanism of wound debridement. Based on these characteristics, the novel L. sericata chymotrypsin-like serine protease appears to be an ideal candidate for the development of topical drugs for wound healing applications.

Selection and Evaluation of Tissue Specific Reference Genes in Lucilia sericata during an Immune Challenge

The larvae of the common green bottle fly Lucilia sericata (Diptera: Calliphoridae) have been used for centuries to promote wound healing, but the molecular basis of their antimicrobial, debridement and healing functions remains largely unknown. The analysis of differential gene expression in specific larval tissues before and after immune challenge could be used to identify key molecular factors, but the most sensitive and reproducible method qRT-PCR requires validated reference genes. We therefore selected 10 candidate reference genes encoding products from different functional classes (18S rRNA, 28S rRNA, actin, β-tubulin, RPS3, RPLP0, EF1α, PKA, GAPDH and GST1). Two widely applied algorithms (GeNorm and Normfinder) were used to analyze reference gene candidates in different larval tissues associated with secretion, digestion, and antimicrobial activity (midgut, hindgut, salivary glands, crop and fat body). The Gram-negative bacterium Pseudomonas aeruginosa was then used to boost the larval immune system and the stability of reference gene expression was tested in comparison to three immune genes (lucimycin, defensin-1 and attacin-2), which target different pathogen classes. We observed no differential expression of the antifungal peptide lucimycin, whereas the representative targeting Gram-positive bacteria (defensin-1) was upregulated in salivary glands, crop, nerve ganglion and reached its maximum in fat body (up to 300-fold). The strongest upregulation in all immune challenged tissues (over 50,000-fold induction in the fat body) was monitored for attacin-2, the representative targeting Gram-negative bacteria. Here we identified and validated a set of reference genes that allows the accurate normalization of gene expression in specific tissues of L. sericata after immune challenge.