Inhibition of eicosanoid signaling leads to increased lipid peroxidation in a host/parasitoid system

Cannabidiol (CBD) Supports the Honeybee Worker Organism by Activating the Antioxidant System

In the experiment, we tested the effect of 30% CBD oil on the activity of the antioxidant system (superoxide dismutase, catalase, glutathione peroxidase, glutathione), the level of total antioxidant capacity, and the concentrations of ions (calcium, magnesium, and phosphorus) in honeybee workers in the hive test. For this purpose, we prepared hives containing all stages of the development of honey bees and started the experiment by adding 200 marked, one-day old bees to each colony (intended for hemolymph collection). In the test, we created three groups (two colonies per group): (1) Experimental with CBD oil mixed with sugar syrup (CSy); (2) experimental with CBD oil on textile strips (CSt); and (3) control with pure sugar syrup only (C). Every week, we collected hemolymph from the marked bees. In the experiment, all antioxidant enzyme activities were higher for the experimental groups CSy and CSt compared to group C. The highest concentrations/levels were obtained for the CSy group. Concentrations of calcium, magnesium, and phosphorus ions were also higher for the experimental groups compared to the C group (the highest concentration for the CSy group). We conclude that CBD oil positively contributes to stimulating the antioxidant system of honeybees.

The Use of Dietary Antifungal Agent Terbinafine in Artificial Diet and Its Effects on Some Biological and Biochemical Parameters of the Model Organism Galleria mellonella (Lepidoptera: Pyralidae)

Diet quality widely affects the survival, development, fecundity, longevity, and hatchability of insects. We used the greater wax moth Galleria mellonella (Linnaeus) to determine the effects of the antifungal, antibiotic terbinafine on some of its' biological parameters. The effects of terbinafine on malondialdehyde (MDA) and protein carbonyl (PCO) contents and the activity of the detoxification enzyme, glutathione S-transferase (GST), in the midgut of seventh-instar larvae of G. mellonella were also investigated. The insects were reared on an artificial diet containing terbinafine at concentrations of 0.001, 0.01, 0.1, and 1 g. The survival rates at all development stages of G. mellonella were significantly decreased at all terbinafine concentrations. The females from a control diet produced 82.9 ± 18.1 eggs; however, this number was significantly reduced to 51.4 ± 9.6 in females given a 0.1 g terbinafine diet. The highest concentration of terbinafine (1 g) completely inhibited egg laying. Terbinafine significantly increased MDA content and GST activity in the midgut tissue of seventh-instar larvae in a dose-dependent manner. Relative to controls, these low dietary concentrations of terbinafine significantly increased midgut PCO content; a 0.1 g terbinafine concentration raised PCO content from 155.19 ± 21.8 to 737.17 ± 36.4 nmol/mg protein. This study shows concentration-dependent effects on the biological traits of the greater wax moth G. mellonella, including the oxidative status and detoxification capacity of the midgut. Low terbinafine concentrations may be possible for use as an antifungal agent in insect-rearing diets.

Azadirachtin acting as a hazardous compound to induce multiple detrimental effects in Drosophila melanogaster

Azadirachtin, a tetranortriterpenoid botanical insecticide, has varied sub-lethal effects against many insect pests, including antifeedant, repellent, and growth regulatory. Despite extensive studies of the mechanisms that underline these physiological effects, little attention has been given to multiple toxic effects of azadirachtin under a coherent concentration, and there is no definitive overarching consensus on its toxicity. Here, we investigated multiple sub-lethal effects induced by 4 mg L^-1 of azadirachtin, which did not elicit antifeedant behavior in Drosophila melanogaster, on metrics of longevity, development, compound eyes and reproduction. Exposure to <20 mg L^-1 azadirachtin did not induce mortality, and 4 mg L^-1 of azadirachtin could shorten lifespan, expression of detoxification genes and activities of related detoxification enzymes were higher. The lower activity of chitinase and higher content of chitin in fruit fly exposed to 4 mg L^-1 azadirachtin could be important in developmental inhibition effects, and ovarian abnormalities and lower fecundity could have resulted from azadirachtin-mediated influences on juvenile hormone and ecdysone that disrupted the endocrine system. Caspase-3, head involution defective and reaper-dependent apoptosis genes may have been responsible for compound eye abnormalities in flies exposed to azadirachtin. Our findings provide important insights to the potential mechanisms of sub-lethal effects of azadirachtin.

A novel calcium-independent phospholipase A2 and its physiological roles in development and immunity of a lepidopteran insect, Spodoptera exigua

Phospholipase A₂ (PLA₂) catalyzes hydrolysis of ester linkage at sn-2 position of phospholipids. At least 15 groups (I-XV) of PLA₂ gene superfamily are associated with various physiological processes such as digestion, secretion, immunity, and maintenance of membrane integrity. This study suggests that various insects encode putative Group VI PLA₂s representing intracellular and calcium-independent PLA₂s (iPLA₂). These insect iPLA₂s are separated into at least two subgroups: iPLA₂A (Group VIA-like) and iPLA₂B (non-Group VIA). Most insects encode genes of iPLA₂B type, although their biological functions are currently unknown. This study predicted a novel iPLA₂ from Spodoptera exigua (a lepidopteran insect) (SeiPLA₂B) and analyzed its physiological functions by RNA interference (RNAi). SeiPLA₂B encodes 336 amino acid sequence with a predicted size of about 36.6 kDa and an isoelectric point at pH 8.61. It possesses a lipase catalytic site, but does not have ankyrin repeats in the amino terminal region. Phylogenetic analysis indicated that SeiPLA₂B was clustered with other Group VI iPLA₂s, in which SeiPLA₂B was closely associated with Group VIF gene while SeiPLA₂A was closely related to Group VIA gene. SeiPLA₂B was expressed in all developmental stages of S. exigua. In larval stage, SeiPLA₂B was expressed in fat body, hemocyte, and epidermis, but not in digestive tract. SeiPLA₂B RNAi significantly reduced PLA₂ enzyme activities and resulted in developmental retardation and immunosuppression. Though RNAi treatment did not significantly change fatty acid composition in fat body lipids, it significantly increased lipid peroxidation. Taken together, our results suggest that SeiPLA₂B plays important roles in the development and immunity of S. exigua.

Chlorine dioxide enhances lipid peroxidation through inhibiting calcium-independent cellular PLA2 in larvae of the Indianmeal moth, Plodia interpunctella

Polyunsaturated fatty acids usually undergo lipid peroxidation induced by reactive oxygen species (ROS). Calcium-independent cellular phospholipase A₂ (iPLA₂) can maintain fatty acid compositions in phospholipids depending on physiological conditions. An insect iPLA₂ (Pi-iPLA₂) was predicted from the transciptome of the Indianmeal moth, Plodia interpunctella. It encodes 835 amino acids. It possesses five ankyrin repeats in the N terminal and patatin lipase domain in the C terminal. Pi-iPLA₂ was expressed in all developmental stages of the Indianmeal moth. In the larval stage, it was expressed in all tissues tested. RNA interference (RNAi) specific to Pi-iPLA₂ was performed using specific double-stranded RNA (dsRNA). It resulted in almost 70% of reduction in gene expression. Under such RNAi condition, P. interpunctella exhibited significant accumulation of lipid peroxidation based on the amount of malondialdehyde. RNAi of Pi-PLA₂ expression also impaired cellular immune response of P. interpunctella. Chlorine dioxide (ClO₂), an insecticidal agent by generating ROS, increased lipid peroxidation in a dose-dependent manner. However, the addition of vitamin E (an antioxidant) reduced the formation of lipid peroxidation. ClO₂ treatment significantly reduced expression of Pi-iPLA₂ but increased lipid peroxidation in larval fat body of P. interpunctella. Furthermore, larvae treated with dsRNA specific to Pi-iPLA₂ were significantly susceptible to ClO₂ treatment. These results suggest that Pi-iPLA₂ plays a crucial role in repairing damaged fatty acids from phospholipids. Our results also suggest that ClO₂ can elevate lipid peroxidation through inhibiting Pi-iPLA₂ expression in addition to direct ROS production.