Determination of Gibberellic Acid (GA3)-Induced Oxidative Stress in a Model Organism Galleria mellonella L. (Lepidoptera: Pyralidae)

Modulation of the antioxidant system by glycoalkaloids in the beetle Tenebrio molitor L

Various factors may affect the antioxidative system in insects, including xenobiotics. Glycoalkaloids (GAs) are plant secondary metabolites produced mainly by the Solanaceae family (nightshades), such as the food crop tomato Solanum lycopersicum L. These compounds exhibit a wide range of biological activities and have attracted increasing interest in the context of potential insecticide properties. Therefore, the aim of the presented study was to analyze the effects of GAs (solanine, chaconine, tomatine, and extracts of tomato leaves) on lipid peroxidation; the expression levels of genes encoding manganese superoxide dismutase (MnSOD), catalase (CAT), and heat shock protein 70 (HSP70); and the enzymatic activity of SOD and CAT in Tenebrio molitor larvae. This species is amodel organism for toxicological and ecophysiological studies and is also a pest of grain storage. The reported changes depend on the GA concentration, incubation time, and type of insect tissue. We observed that the tested GAs affected MnSOD expression levels, increased SOD activity in the fat body, and reduced enzyme activity in the gut. The results showed that CAT expression was upregulated in the fat body and that the enzymatic activity of CAT in the gut was greater in the treated group than in the control group. Moreover, GAs affected HSP70 expression and malondialdehyde levels in both tested tissues. This research contributes to our knowledge about the effects of GAs on the antioxidative system of T. molitor beetles. As efficient antioxidative system functioning is necessary for survival, the tested components may be targets of potential bioinsecticides.

Immunosuppressive effect of Plantago major on the innate immunity of Galleria mellonella

Greater plantain (Plantago major), a medicinal plant species, is used in folk medicine for the treatment of various diseases in many countries of the world. Different studies have shown that the bioactive components contained in the plant have a dual effect. It was also reported that in vivo and in vitro studies showed different results. The aim of the study was to determine the effects of P. major extract on the hemocyte-mediated and humoral immune responses of the invertebrate model organism Galleria mellonella, which is widely used in immune studies. In the evaluation of these effects, total hemocyte count, encapsulation, melanization, phenoloxidase, superoxide dismutase, catalase, malondialdehyde and total protein parameters were evaluated. The results of the study showed that the total hemocyte count did not change, that the encapsulation responses decreased, that the melanization responses and phenoloxidase activity increased and that the superoxide dismutase activity decreased. As a result, it was determined that high doses of P. major had negative effects on cell-mediated immunity and antioxidant defence and positive effects on melanization. High doses and continuous use of P. major may have negative effects on living things.

The mitigating effect of Spirulina (Arthrospira platensis) on the hemotoxicity of gibberellic acid on juvenile tilapia (Oreochromis niloticus)

The use of plant growth regulators has led to environmental contamination of water bodies that occur adjacent to agricultural areas. Some of these chemicals are bioactive, not only to plants, but also to non-target exposed biota, namely of the aquatic compartment. Previous work demonstrated the establishment of hepato- and nephrotoxic effects in juvenile tilapia (Oreochromis niloticus) exposed via aquatic media to gibberellic acid (GA3), which is among the most used plant growth regulators, in agricultural practices. Here, we investigated the effect of GA3 on hematological indices, poikilocytosis, nuclear abnormalities, and genotoxic indices measured in Nile tilapia (Oreochromis niloticus), as well as the putative protective effects of dietary supplementation of Spirulina (Arthrospira platensis). Fish were evenly assorted into 5 groups: group I served as a control, and groups II-V were fed diets supplemented with Spirulina at rates of 0 g/kg, 5 g/kg, 20 g/kg, and 100 g/kg, respectively, for 2 months before being exposed to 150 mg/L GA3. The results revealed that GA3 exposure decreased significantly all hematological indices (P < 0.05), except leucocytes and mean corpuscular hemoglobin concentration (MCHC), compared to the control group (P > 0.05). GA3 exposure increased significantly the percentage of nuclear abnormalities, altered erythrocytes and the percentages of tail DNA, compared to the control group (P < 0.05). Spirulina supplementation restored the hematological, poikilocytosis, nuclear abnormalities, and the percentages of tail DNA to near normal levels. The 100 g/kg SP treatment was the most effective in attaining such effect, showing concentration-dependency. The present study reinforces our findings of the toxicity of GA3 on O. niloticus and suggests that the addition of Spirulina to fish diet can mitigate the hemotoxic effects of GA3.

Phytohormone Profile of Medicago in Response to Mycorrhizal Fungi, Aphids, and Gibberellic Acid

Although gibberellic acid (GA) is widely used in agriculture, it is unclear whether exogenous GA makes aphid-infested, mycorrhizal plants more susceptible to herbivory. This study investigates the role of GA in modulating defenses in barrel medic plants (Medicago truncatula) that are infested with pea aphids (Acyrthosiphon pisum) and colonized by the beneficial symbiont Rhizophagus intraradices. Mock- and R. intraradices-inoculated potted plants were grown in a topsoil: sand mix for 42 days and were treated with GA or solvent. Subsequently, plants were exposed to herbivory or no aphid herbivory for 36 h and 7 days. Afterwards, plant growth parameters, aphid fitness, and foliar phytohormone concentrations were measured. The results revealed that GA regulates plant defenses during arbuscular mycorrhizal (AM) fungus–plant–aphid interactions as aphids that fed for 7 days on mycorrhizal, GA-untreated plants weighed more than those that fed on mycorrhizal, GA-treated plants. No major differences were detected in phytohormone levels at 36 h. Overall, mycorrhizal plants showed more shoot biomass compared to non-mycorrhizal controls. The arbuscule density and fungal biomass of R. intraradices were not altered by exogenous GA and aphid herbivory based on molecular markers. This study indicates that exogenous GA may help reduce aphid fitness when feeding on mycorrhizal plants.

Fat on plastic: Metabolic consequences of an LDPE diet in the fat body of the greater wax moth larvae (Galleria mellonella)

The caterpillar larvae of the greater wax moth (Galleria mellonella) are avid plastivores, as when provided a diet of low-density polyethylene (LDPE) they actively feed on it. Recent work has highlighted the importance of their microbiome in the putative biodegradation of this plastic polymer, though the impact of plastic metabolism on the insect host is less clear. In the present study, we undertook an integrative approach spanning all levels of biological organization to explore the effects of a plastic diet on the metabolic physiology of this animal model of plastic biodegradation. We demonstrate that an LDPE diet is not sufficient to maintain optimal larval growth and survival. In addition, we confirm that plastic fed waxworms retain their fat body lipid stores in a manner proportional to their individual polyethylene consumption suggesting a direct effect of LDPE biodegradation. At the functional level, the oxidative capacity of the fat body of LDPE-fed larvae is maintained reflecting unaltered metabolic function of the tissue. Finally, metabolomic analyses confirmed fat body lipid stores maintenance in LDPE-fed worms, but uncovered various other nutritional deficiencies. Overall, this work unveils novel insights in the complex interplay between LDPE biodegradation and the metabolic physiology of this model plastivore.

Impacts of n-acetyl cysteine on gibberellic acid-induced testicular dysfunction through regulation of inflammatory cytokines, steroid and antioxidant activity

In agriculture, gibberellic acid (GA3) is commonly used with extreme dangers for public health. The current research evaluates the improving effects of n-acetyl cysteine (NAC, 150 mg/kg bw) co-administered with GA3 (55 mg/kg bw) mediated testicular injury. Twenty-four male albino rats were split into 4 groups: Negative control (CNT), NAC group, positive GA3 group and protective group, co-administered NAC plus GA3. On day 21, rats were anesthetised then euthanised by decapitation. Blood samples were collected; testicular samples were taken for semen analysis, serum chemistry, RNA extraction, histological and antioxidants markers examination. Our results revealed a significant decline p < .05 of catalase level and total antioxidant capacity. There was a substantial rise of MDA concentration in GA3-treated rats along with a considerable decrease of the antioxidant markers (SOD, GSH) and serum male reproductive hormones. In GA3-treated rats, an overexpression of the inflammatory cytokines (TNF-α, IL-1β) and anti-inflammatory cytokine IL-10 with boost mRNA expression of nuclear factor-kappa (NF_k B) were confirmed. There was downregulation of steroidogenesis genes and decrease in sperm quality and concentration with an increase in sperm abnormalities, all were reported in GA3-treated rats. NAC treatment significantly increased the antioxidant state, testicular function beside structural germ cell and seminiferous tubules histology accompanied by upsurge of steroidogenic mRNA expressions (P450scc and 3β-HSD) and downregulated the pro-inflammatory cytokines mRNA expression (TNF-α, IL-1β). These results confirm the antioxidant capability of NAC and afford robust evidence about the ameliorative effect of the NAC to attenuate the testicular injury induced by GA3 through modulation of the antioxidant defence system, steroidogenic and pro-inflammatory cytokines mRNA expression.