The Changes in Mitochondrial Morphology and Physiology Accompanying Apoptosis in Galleria mellonella (Lepidoptera) Immunocompetent Cells during Conidiobolus coronatus (Entomophthorales) Infection

The activation of caspases in immunocompetent cells is an important infection factor of the pathogenic fungus Conidiobolus coronatus (Entomophthorales: Ancylistaceae)

Apoptosis is a mechanism commonly used by pathogenic fungi to inhibit the host's immune response. One opportunistic pathogen is Conidiobolus coronatus, which causes fungal infection in mammals and insects. In a study, larvae of Galleria mellonella were exposed to the pathogen for 24 h. After this exposure, some larvae were used for hemolymph collection (F24), while others were incubated for an additional 24 h (F48). The activity of caspase-9 and caspase-3-like proteins in hemocytes was measured using a colorimetric method. The changes in caspase concentration were calculated using ELISA tests. Immunocytochemical analyses were employed to show changes in the levels of the examined proteins in both their pro- and active forms. Fluorescence microscopy was used to detect changes in cultured hemocytes and flow cytometry analysis was conducted to detect both forms of caspases in freshly collected hemocytes. To evaluate the effect of fungal infection, caspase inhibitors (Z-DEVD-FMK and Z-LEHD-FMK) were injected into the larvae, and their impact on insect development and resistance to fungal infection was determined. The exposure of larvae to the entomopathogen increased the detection levels, concentrations, and activity of both caspase-like proteins in hemocytes during fungal infection. The research has indicated that inhibition of these proteins disrupts larval development and increases resistance to infection. These results suggest that apoptosis might be an important mechanism for a pathogen to inhibit the insect immune response. Given the similarities between insects' and mammals' innate immune responses, the presented results may indicate a potential mechanism of fungal pathogenicity in both groups.

The flavouring agent, 2-octenoic acid kills Galleria mellonella (Lepidoptera: Pyralidae) by affecting their immunocompetent cells and cuticular FFA profiles

This study investigates the effects of the naturally occurring flavouring agent, trans-2-octenoic acid, on the insect model Galleria mellonella by examining its impact on immunocompetent cells and free fatty acid (FFA) profiles in the cuticle. The value of LD50 for 2-octenoic acid has been calculated as 9.66 µg/mg of insect body mass, this value is outside the GHS scale, indicating that the compound is unlikely to cause acute toxicity after dermal application and is safe for humans and mammals. Thetreatment with 2-octenoic acid caused several changes in the insect defence mechanismes, viz. changes in cuticular FFA profiles and death of immunocompetent cells. In larvae, topical treatment of 2-octenoic acid increased the concentration of cuticular FFAs, particularly C6:0 (245 times higher), C15:0 (110 times higher), and C16:1 (1608 times higher), and 2-octenoic acid (C8:1) accumulated significantly on the surface of the cuticle. In adults, treatment resulted in lower cuticular C8:1concentrations than in larvae, which might indicate that 2-octenoic acid penetrates more effectively through the adult cuticle. The 2-octenoic acid application demonstrated considerable cytotoxicity against insect cell line Sf9 and G. mellonella hemocytes, with both in vivo and in vitro treatment. Our findings contribute to the broader understanding of how synthetic and naturally occurring chemicals may interact with the immune and physiological systems of insects, particularly focusing on G. mellonella as a model organism for toxicological studies. Given the increasing interest in the ecological and physiological impacts of food additives, our research provides novel insights into the biological interactions of 2-octenoic acid and its potential role as an insecticide.

The flavouring agent, 2-octenoic acid kills Galleria mellonella larvae by affecting the cellular and humoral elements of insect immunological system

Larvae of Galleria mellonella are well known for their parasitisation of honeybees, so developing new methods of controlling the pest population is an important issue. The present research examined the immunotoxic effects of 2-octenoic acid against wax moth larvae. The last instar larvae were used for all experimental analyses. The tested fatty acid doses LD50 and LD100 (9.66 µg/mg and 11.72 µg/mg of body mass) were applied topically to insects under in vivo conditions and the hemolymph was collected after 24 and 48 h. To check the in vitro impact of the 2-octenoic acid, the examined fatty acid was given directly to the cultured hemocytes (to a final concentration: 0.33 and 0.16 µg/µl) and incubated for 24 and 48 h. Current research using fluorescence microscopy and spectrofluorimetric measurements indicates the death of immunocompetent cells via the apoptosis pathway. Moreover, it shows the activation of caspases and an increase in the level of reactive oxygen/nitrogen damage after both in vivo and in vitro treatment of 2-octenoic acid. This points to the impact of both cellular and humoral elements on the immunological response to the toxic compound. Hence, 2-octenoic acid seems to have significant potential as an insecticide while being safe for humans and the environment. Therefore, further research into its potential is warranted.

The multifunctional role of IFN-γ in Galleria mellonella (Lepidoptera) immunocompetent cells

Cytokines are highly conserved between mammals and insects. The present study examines the multiple effects of interferon-gamma (IFN-γ) application on the immunological defence mechanisms of Galleria mellonella larvae, invertebrates which are gaining popularity as a replacement for mammalian research models in immunological studies. G. mellonella hemolymph is known to contain an IFN-γ homolog that shares 33 % similarity with its mammalian analogue, and its level in insect hemocytes increases during exposition to entomopathogenic fungus Conidiobolus coronatus. The present research examines the impact of IFN-γ on larval development, the effectiveness of fungal infection, and the morphology and physiology of wax moth immunocompetent cells. Treatment with IFN-γ enhanced wound healing, chemotaxis activity and hemocyte impedance, while reducing hemocyte phagocytosis and oxidative stress in cultured immunocompetent cells; it also appears to increase the levels of Jak-2- and NF-κB-like molecules in hemocytes. Our findings suggest that IFN-γ demonstrated considerable similarity between mammals and humans, thus further demonstrating the evolutionary conservatism of cytokines.

Octanoic acid kills Lucilia sericata (Diptera: Calliphoridae) by affecting two major defence systems: cuticular free fatty acids and immunocompetent cells

This work examines the insecticidal activity of octanoic acid (C8:0), a short-chain fatty acid detected in entomopathogenic fungus - Conidiobolus coronatus medium, against Lucilia sericata larvae and adults. The LD50 value was calculated as 3.04±0.26 µg/mg (3040 mg/kg) of insect body mass, which places the compound in category 5 of acute toxicity (slightly hazardous). The presented research also describes its probable mechanism, with a particular focus on changes in two main insect defense mechanisms: (1) the composition of the cuticle (GC-MS analysis) and (2) immunocompetent cells (microscopic analysis of cultured hemocytes). More precisely, octanoic acid application resulted in changes in cuticular free fatty acid (FFA) profiles in both adults and larvae; generally, treatment increased short-chain FFAs, and a decrease of middle- and long-chain FFAs. Both in vivo and in vitro applications of octanoic acid resulted in vacuolisation, disintegration, and destruction of nets formed by plasmatocytes. As the compound has also previously been found to be toxic against Galleria mellonella, it appears to have lethal potential against insects in both the Orders Diptera and Lepidoptera, indicating it may have strong entomopathogenic potential. It is worth noting that octanoic acid is approved as a food additive with well-documented insecticidal activity, and hence may be a valuable component in the design of new insecticides that are safe for both humans and the environment.

Mitochondrial Melatonin: Beneficial Effects in Protecting against Heart Failure

Cardiovascular disease is the cause of physical infirmity and thousands of deaths annually. Typically, during heart failure, cardiomyocyte mitochondria falter in terms of energy production and metabolic processing. Additionally, inflammation and the accumulation of non-contractile fibrous tissue contribute to cardiac malfunction. Melatonin, an endogenously produced molecule, experimentally reduces the initiation and progression of atherosclerotic lesions, which are often the basis of coronary artery disease. The current review critically analyzes published data related to the experimental use of melatonin to forestall coronary artery pathologies. Collectively, these studies document melatonin's anti-atherosclerotic actions in reducing LDL oxidation and triglyceride levels, lowering endothelial malfunction, limiting adhesion molecule formation, preventing macrophage polarization to the M1 pro-inflammatory phenotype, changing cellular metabolism, scavenging destructive reactive oxygen species, preventing the proliferation and invasion of arterial smooth muscle cells into the lesioned area, restricting the ingrowth of blood vessels from the vasa vasorum, and solidifying the plaque cap to reduce the chance of its rupture. Diabetic hyperglycemia, which aggravates atherosclerotic plaque formation, is also inhibited by melatonin supplementation in experimental animals. The potential value of non-toxic melatonin as a possible inhibitor of cardiac pathology in humans should be seriously considered by performing clinical trials using this multifunctional molecule.

The Entomopathogenic Fungus Conidiobolus coronatus Has Similar Effects on the Cuticular Free Fatty Acid Profile of Sensitive and Resistant Insects

The mechanisms underlying the recognition of a susceptible host by a fungus and the role of cuticular compounds (CCs) in this process remain unclear; however, accumulated data suggest that this is influenced to a great degree by cuticular lipids. Two insect species differing in their sensitivity to fungal infection, viz. the highly sensitive Galleria mellonella Linnaeus (Lepidoptera: Pyralidae) and the resistant Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae), exhibited significant qualitative and quantitative changes in cuticular free fatty acid (FFA) profiles after exposure to Conidiobolus coronatus (Constantin) Batko (Entomopthorales). Despite being systematically distant, leading different lifestyles in different habitats, both insect species demonstrated similar changes in the same FFAs following exposure to the fungus (C12:0, C13:0, C14:0, C15:0, C16:1, C16:0, C18:1, C18:0), suggesting that these are involved in a contact-induced defense response. As it was not possible to distinguish the share of FFAs present in the conidia that were attached to the cuticle from the FFAs of the cuticle itself in the total number of extracted FFAs, further research is necessary.