Lethal and sublethal effects of cantharidin on the life history traits and population parameters of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Network toxicology, molecular docking technology, and experimental verification revealed the mechanism of cantharidin-induced testicular injury in mice

As a protein kinase inhibitor, cantharidin (CTD) exhibits antitumor activities. However, CTD is highly toxic, thereby limiting clinical applications. Moreover, relatively few studies have investigated CTD-induced reproductive toxicity, thus the underlying mechanism remains unclear. In this study, the toxic effects of CTD on mouse testis were confirmed in vivo and the potential mechanism was predicted by network toxicology (NT) and molecular docking technology. Proteins involved in the signaling pathways and core targets were verified. The results showed that different concentrations of CTD induced weight loss increased the testicular coefficient, and caused obvious pathological damage to testicular cells. The NT results showed that the main targets of CTD-induced testicular injury (TI) included AKT1, Caspase 3, Bcl-2, and Bax. The results of pathway enrichment analysis showed that CTD-induced TI was closely related to apoptosis and the PI3K/AKT and HIF-1 signaling pathways. Molecular docking methods confirmed high affinity between CTD and key targets. Western blot analysis showed that CTD inhibited expression of PI3K, AKT, and the anti-apoptotic protein Bcl-2, while promoting expression of the pro-apoptotic proteins Bax and Caspase 3. These results suggest that CTD-induced TI involves multiple targets and pathways, and the underlying mechanism was associated with inhibition of the apoptosis-related PI3K/AKT signaling pathway.

Cantharidin-induced toxic injury, oxidative stress, and autophagy attenuated by Astragalus polysaccharides in mouse testis

Cantharidin (CTD) is a chemical constituent derived from Mylabris and has good antitumor effects, but its clinical use is restricted by its inherent toxicity. However, few researches have reported its reproductive toxicity and mechanisms. This study aims to assess CTD's toxicity on mouse testes and the protective effect of Astragalus polysaccharides (APS). Briefly, biochemical analysis, histopathology, transmission electron microscopy, immunohistochemistry, and Western blotting were used to evaluate the oxidative damage of mouse testicular tissue after exposure to CTD and treatment by APS. Our research suggests a dramatic decrease in testicular index and serum testosterone levels after CTD exposure. The testis showed obvious oxidative damage accompanied by an increase in mitochondrial autophagy, the Nfr2-Keap1 pathway was inhibited, and the blood-testis barrier was destroyed. Notably, these changes were significantly improved after APS treatment. The internal mechanisms of APS ameliorate CTD-induced testicular oxidative damage in mice may be closely connected to regulatory the Nrf2-Keap1 signaling pathway, restraining autophagy, and repairing the blood-testis barrier, providing theoretical support for further study on the reproductive toxicity mechanism of CTD and clinical treatments to ameliorate it.

The Detoxification Enzymatic Responses of Plutella xylostella (Lepidoptera: Plutellidae) to Cantharidin

Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most destructive pests of Brassicaceae vegetables. Cantharidin is an insect-derived defensive toxin, which has been reported to have toxicity to a variety of pests and especially lepidopteran pests. Although the toxicity of cantharidin on P. xylostella has been demonstrated, there is little information available on the specific detoxification response of P. xylostella against cantharidin. This study investigates the enzymatic response (including serine/threonine phosphatases [PSPs], carboxylesterases [CarEs], glutathione-S-transferases [GSTs], and cytochrome P450 monooxygenases [P450]) in P. xylostella to the sublethal and low lethal concentrations of cantharidin (LC10 and LC25). Results showed that the inhibitory activity of PSPs was increased and then decreased in vivo, while PSPs activity could be almost completely inhibited in vitro. Interestingly, the activities of detoxification enzymes (GST, CarE, and P450) in P. xylostella displayed a trend of decreasing and then increasing after exposure to the two concentrations of cantharidin. Notably, the increase in P450 enzyme activity was the most significant. The increasing trend of detoxification enzyme activity was congruent with the recovery trend of PSPs activity. This study contributes to our understanding of the detoxification mechanism of cantharidin in P. xylostella and helps in the further development of biogenic agents.

Sublethal Effects of Chlorantraniliprole on Spodoptera litura (Lepidoptera: Noctuidae) Moth: Implication for Attract-And-Kill Strategy

The integrated use of plant-derived volatile attractants and synthetic insecticides in attract-and-kill programs is a useful tool for integrated pest management programs reducing pesticide input. Efficient alternative insecticides are critically needed to replace methomyl, which has been banned on cruciferous vegetables in China because it is also highly toxic to nontarget organisms. In the present study, among 15 commonly used insecticides were screened for toxicity against S. litura moths, where chlorantraniliprole, flubendiamide, and emamectin benzoate was found to have the highest levels of toxicity (LC₅₀ of 0.56, 3.85, and 6.03 mg a.i. L⁻¹ respectively). After exposure to the low lethal concentration LC₅₀ of chlorantraniliprole, fecundity of the moths was substantially reduced. Egg-hatching was lower for LC₂₀- and LC₅₀-treated moth pairs than for untreated control pairs. Net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) were significantly reduced in LC₅₀♀ × LC₅₀♂ cohorts. Larval mortality was significantly higher in subsequent generations in pairs of LC₅₀-treated moths. Chlorantraniliprole, which was most toxic and had significant sublethal effects on moths, can be used as an alternative insecticide to methomyl in the attracticide for controlling S. litura moths, and the LC₅₀ indicated a high potential for efficacy in the control S. litura through attract-and-kill schemes.

The Inhibition of Serine/Threonine Protein Phosphatase Type 5 Mediates Cantharidin Toxicity to Control Periplaneta americana (L.)

The American cockroach, Periplaneta americana (L.), is a notorious urban pest. It has developed insecticidal resistance to commonly used insecticides. Cantharidin (CTD) is a defensive toxin derived from blister beetles. It has been verified to have insecticidal toxicity in a range of pests. In this study, we determined the ingestion toxicity of CTD and norcantharidin (NCTD) to P. americana to test whether they had the potential to be effective against P. americana. Bioassays revealed that CTD produces toxicity against P. americana. The median lethal concentration (LC₅₀) value of CTD was 50.92 μg/mL, while NCTD displayed nearly no toxicity against P. americana. The inhibition assays of serine/threonine protein phosphatases (PSPs) in P. americana indicated that CTD and NCTD could inhibit PSPs. The value of the half maximal inhibitory concentration (IC₅₀) of CTD was 7.21 ± 0.94 μM, whereas that of NCTD was higher, at 31.65 ± 3.87 μM. Furthermore, the inhibition effect of CTD on the serine/threonine protein phosphatase type 5 of P. americana (PaPP5) was superior to that of NCTD. Specifically, the IC₅₀ of CTD reached 0.39 ± 0.04 μM, while the IC₅₀ of NCTD was 1.87 ± 0.23 μM. This study paves the way for insect-derived agents (CTD) to be applied toward controlling P. americana and contributes to the development of novel insecticides based on PP5 as a target.

Effects of Cantharidin and Norcantharidin on Larval Feeding and Adult Oviposition Preferences of the Diamondback Moth (Lepidoptera: Plutellidae)

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a destructive insect pest of cruciferous plants that has developed resistance to almost every listed commercial insecticide. Cantharidin as an animal-derived biopesticide is a natural defensive compound produced by Meloidae insects with toxicity to many insects including P. xylostella. Norcantharidin is an important substitute of cantharidin and has similar insecticidal activities to cantharidin. Although the toxicity of cantharidin and norcantharidin to P. xylostella has been reported, little research has focused on the effects of cantharidin or norcantharidin on the behavior of P. xylostella. In this study, we investigated the feeding behavior of third-instar larvae and the oviposition preference of adult P. xylostella in order to explore the effects of different concentrations of cantharidin and norcantharidin. Results show that cantharidin and norcantharidin have antifeedant effect on P. xylostella larvae. The values for AFC50 were 13.0228 and 149.4210 mg/ml, respectively. Furthermore, the oviposition deterrence rate of cantharidin on P. xylostella ranged from 49.37 to 58.24% and that of norcantharidin was from 20.88 to 33.33%. These results suggest cantharidin and norcantharidin may have repellent and antifeedant effect on P. xylostella, which could contribute toward using biopesticides to manage P. xylostella and may provide a new strategy for integrated pest management.

Biological Evaluation of Endothall, a Dicarboxylic Acid Analog of Norcantharidin, and Cantharidin on Oriental Leafworm, Spodoptera litura (Lepidoptera: Noctuidae)

Cantharidin is a highly potent toxin produced by insects belonging to the order Coleoptera and family Meloidae. The insecticidal activity of cantharidin against different orders of insects has been well documented. Although it is highly effective, its extraction and synthesis is very tedious. Consequently, much work is underway to synthesize the bioactive analogs of norcantharidin and study their relative structures. In this study, we investigate the acute and chronic toxicological effects of cantharidin and endothall, an analog of norcantharidin, using an age-stage-based two-sex life table methodology. Results reveal the acute toxicity of these compounds to Spodoptera litura Fabricius (Lepidoptera: Noctuidae), with the LC50 of cantharidin being 2.10 and endothall being 3.72 ppm, after 72 h posttreatment. Although both the compounds negatively affected the intrinsic rate of population increase (r), finite rate of increase (λ), net reproduction rate (R0), mean generation time (T), doubling time (DT), relative fitness (Rf), biotic potential, and longevity, cantharidin was slightly more effective. Among the reproductive parameters, fecundity was severely affected by cantharidin, which reduced offspring to 42 compared to 528 per female in the control cohort. Both cantharidin and endothall caused similar physiological changes such as weight reduction, wing malformation, and pupal deformities. These findings demonstrate that both cantharidin and endothall are highly toxic to S. litura, particularly in their chronic effects on population parameters. This will help us to understand the biological and ecological interactions in agricultural cropping systems and how their application will modify insect herbivory.

Toxicity and sublethal effects of fluralaner on Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

The increasing occurrence of resistance to chemical insecticides in insect pest populations is a serious threat to the integrity of current pest management strategies, and exploring new alternative chemistries is one important way to overcome this obstacle. Fluralaner, as a novel isoxazoline insecticide, has broad spectrum activity against a variety of insect pests, but little data is available about its effect on Lepidopterans. The effects of fluralaner on Spodoptera litura Fabricius, a widespread and polyphagous pest, were evaluated in the present study. Our results showed younger larvae were more susceptible to fluralaner treatment, but feeding and topical applications were similarly effective in 3rd instar larvae. Synergism assays indicated that piperonyl butoxide (PBO) could increase the toxicity of fluralaner to S. litura to a certain degree and P450 may be involved in the detoxification of fluralaner in vivo. Sublethal developmental effects included reduced larval body weight, decreased pupation and emergence, and notched wings in adults, accompanied by changes in the transcript levels of chitinase 5 (CHT5) and juvenile hormone acid methyltransferase (Jhamt), genes vital for insect development. Above results manifested that fluralaner is highly toxic to S. litura larvae via either topical or oral application and provide an indication of how this insecticide is metabolized in vivo. Further, our results provided a foundation for further development of fluralaner as a new tool in insect pest management.

Toxicity and Sublethal Effects of Cantharidin on Musca domestica (Diptera: Muscidae)

The house fly, Musca domestica L. (Diptera: Muscidae), is a major pest of medical and veterinary importance all over the world. Management efforts for house flies are usually compromised owing to their resistance to many groups of conventional insecticides. Cantharidin, a natural toxin produced by meloid beetles, is a biopesticide with a reported toxicity to some insect pests including house flies. However, the effects of cantharidin on biological and fitness parameters of house flies have not yet been investigated. In the present study, we investigated the toxicity and sublethal effects of cantharidin on biological parameters of house flies for two consecutive generations. The results revealed that the values of LC50, LC25, LC10, and LC2 against house flies were to be 2.45, 1.23, 0.66, and 0.30 mg/liter, respectively. Sublethal effects of these concentrations on the development and reproduction parameters of house flies revealed that cantharidin reduced population growth by affecting pupation rate, adult emergence, and by lengthening developmental time. The female ratio, fecundity, egg hatching, and survival of adult flies were significantly reduced at LC2, LC10, LC25, and LC50 of cantharidin when compared with the control group. Furthermore, the increase in concentration of cantharidin had a significant effect on reducing the mean values of mean relative growth rate, net reproductive rate (Ro), intrinsic rate of natural increase (rm), and biotic potential (bp). In conclusion, the results of this study revealed the toxicity of cantharidin against house flies and the adverse effects of sublethal concentrations on biological parameters which may have positive implications for effective management of house flies.

Effects of Ethacrynic Acid Addition to Diet on Fitness and Development in the Psocid Liposcelis bostrychophila Badonnel

Fertility life table provides a comprehensive description of arthropod population dynamics by the estimation of parameters about arthropod population growth potential. It can also clarify the sublethal effects of chemicals on insects. Ethacrynic acid (EA), an inhibitor of glutathione S-transferases, is a diuretic compound that has been confirmed to modulate drug resistance in organisms. In this study, the effects of EA on growth and development of Liposcelis bostrychophila Badonnel were investigated in the laboratory to explore the potential possibilities of EA as an active agent to manage insecticide-resistant psocids. The treatment of psocids was obtained by feeding on the routine diet containing 3% EA for three successive generations, and psocids on routine diet served as control. The results indicated that EA possessed some negative effects on the life-table parameters of the psocid in F1 and F2 generations. The addition of EA to diet stunted psocids growth by lengthening development time and increasing mortality with a greater effect in the F2 generation. In the third generation of psocids on EA diet, it seemed there was a return to normal. Psocid fitness was influenced by addition of EA to standard diet. Using rm values, the fitness for EA diet in F1, F2, and F3 compared with the counterpart of routine diet was calculated as 0.80, 0.74, and 0.87, respectively.

Lethal and Sublethal Effects of Cantharidin on Development and Reproduction of Plutella xylostella (Lepidoptera: Plutellidae)

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a major pest of cruciferous vegetables throughout the world. Cantharidin, a natural toxin isolated from beetles in the families Meloidae and Oedemeridae, has been reported to be toxic to some pests, including the diamondback moth. However, the effects of cantharidin, especially its sublethal effects on development and reproduction of diamondback moth, are less known. In this study, we investigated the sublethal effects of cantharidin at LC2 (0.41 mg liter(-1)), LC10 (1.33 mg liter(-1)), LC25 (3.38 mg liter(-1)), and LC50 (9.53 mg liter(-1)) on development and reproduction parameters of two consecutive diamondback moth generations. The results indicated that cantharidin reduced population growth by decreasing its pupation rate, pupal weight, and adult emergence, and by delaying its development. Furthermore, the duration of the female preoviposition period increased, while the oviposition and postoviposition periods, fecundity, and survival rates of the offspring decreased. The peaks of age-specific fecundity in LC10, LC25, and LC50 treatment groups lagged behind the control group. The mean values of the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were significantly lower than those of the control, and the mean generation time (T) was prolonged. The present study demonstrates that cantharidin exhibits significant adverse effects on the population dynamics of diamondback moth, leading to fitness disadvantages.

Chronic Sublethal Effects of Cantharidin on the Diamondback Moth Plutella xylostella (Lepidoptera: Plutellidae)

The diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), is a major pest of cruciferous vegetables worldwide. Cantharidin, a natural toxin isolated from blister beetles, has been reported to be toxic to P. xylostella. However, little is known on the chronic sublethal effects of cantharidin on this species. In this study, we assessed the changes of susceptibility, development, reproduction and other demographic parameters in both the selected P. xylostella strain (Sub, selected by LC25 cantharidin for consecutive 12 generations) and the revertant strain (SubR, derived from the Sub strain without being exposed to cantharidin for 12 generations). Results revealed that the two strains maintained a relatively high-level susceptibility to cantharidin. Severe adverse effects on the population dynamics and fitness in Sub strain were observed. In addition, repeated exposure of P. xylostella to sublethal concentration of cantharidin resulted in negative effects on adult performance and deformities in adults. Although morphologically normal for individuals, the SubR strain exhibited a disadvantage in population growth rate. Our results showed that sublethal concentration of cantharidin exhibited severe negative effects on population growth for longtime. These findings would be useful for assessing the potential effects and risk of cantharidin on P. xylostella and for developing effective integrated pest management.

The Toxicology and Biochemical Characterization of Cantharidin on Cydia pomonella

Cantharidin, a natural toxin produced by beetles in the families Meloidae and Oedemeridae, reported to be toxic to some pests, is being developed as a biopesticide in China. This study evaluates the toxicity and biochemical characterization of cantharidin on the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), an economically important fruit pest, under both laboratory and field conditions. Laboratory dose response bioassays showed that the LC50 value of cantharidin against neonate larvae was 0.057 mg ml(-1). Exposure of the larvae to 0.024 and 0.057 mg ml(-1) of cantharidin resulted in significant reduction in larval body weight. Neonate larvae exposed to LC10 of cantharidin showed increased glutathione S-transferase activity and significantly reduced the carboxylesterase and cytochrome P450-dependent mixed-function oxidase activities. Results also showed 16 and 25% ovicidal activity at concentrations of 0.057 and 0.14 mg ml(-1) of cantharidin, respectively. Field trials demonstrated cantharidin has a significant effect on both the first and second generations of C. pomonella larvae, but it exhibits a lower control efficiency than the chemical reference emamectin benzoate. Cantharidin may be considered a valuable tool for the control of codling moth.