3-Bromopyruvate-induced glycolysis inhibition impacts larval growth and development and carbohydrate homeostasis in fall webworm, Hyphantria cunea Drury

Chitinase inhibition induces transcriptional dysregulation altering ecdysteroid-mediated control of Spodoptera frugiperda development

Chitinases and ecdysteroid hormones are vital for insect development. Crosstalk between chitin and ecdysteroid metabolism regulation is enigmatic. Here, we examined chitinase inhibition effect on Spodoptera frugiperda ecdysteroid metabolism. In vitro studies suggested that berberine inhibits S. frugiperda chitinase 5 (SfCht5). The Berberine feeding resulted in defective S. frugiperda development. Berberine-fed insects showed higher SfCht5 and Chitinase 7 expression and cumulative chitinase activity. Chitinase inhibition led to overexpression of chitinases, ecdysteroid biosynthesis, and responsive genes. SfCht5 silencing and overexpression resulted in ecdysone receptor deregulation. Transcription factors, like Broad Complex Z4, regulate the ecdysteroid metabolism and showed high expression upon berberine ingestion. Broad Complex Z4 binding in 5' UTR of Ecdysone receptor, SfCht5, Chitinase 7, Phantom, Neverland, and other ecdysteroid biosynthesis genes might lead to their upregulation in berberine-fed insects. As a result, berberine-fed insects showed ecdysone overaccumulation. These findings underscore chitinase activity's impact on ecdysone biosynthesis and its transcriptional crosstalk.

FDP-Na-induced enhancement of glycolysis impacts larval growth and development and chitin biosynthesis in fall webworm, Hyphantria cunea (Lepidoptera: Arctiidae)

Fructose 1, 6-diphosphate (FDP) is an endogenous intermediate in the glycolytic pathway, as well as an allosteric activator of phosphofructokinase (PFK). Based on the role in promoting glycolysis, FDP has been widely used as a therapeutic agent for mitigating the damage of endotoxemia and ischemia/reperfusion in clinical practice. However, the effect of exogenous FDP-induced glycolysis activation on insect carbohydrate metabolism and chitin synthesis remains largely unclear. Here, we investigated for the first time the effects of FDP-Na, an allosteric activator of PFK, on the growth and development of Hyphantria cunea larvae, a serious defoliator in agriculture and forestry, especially on glycolysis and chitin synthesis. The results showed that FDP-Na significantly restrained the growth and development of H. cunea larvae and resulted in larval lethality. After treatment with FDP-Na, hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were significantly activated, and HcHK2, HcPFK, HcPK were dramatically upregulated, which suggested that FDP-Na enhanced glycolysis in H. cunea larvae. Meanwhile, FDP-Na also distinctly impacted chitin biosynthesis by disturbing transcriptions of genes in the chitin synthesis pathway, resulting in changes of chitin contents in the midgut and epidermis of H. cunea larvae. Therefore, we considered that FDP-Na caused the growth and development arrest, and impacted chitin biosynthesis, probably by disturbing in vivo glycolysis and carbohydrate metabolism in H. cunea larvae. The findings provide a new perspective on the mechanism by which glycolysis regulates insect growth and development, and lay the foundation for exploring the potential application of glycolysis activators in pest control as well.

Alteration of antioxidant status, glucose metabolism, and hypoxia signal pathway in Eirocheir sinensis after acute hypoxic stress and reoxygenation

Dissolved oxygen (DO) is crucial for the survival of Chinese mitten crab (Eirocheir sinensis); low DO levels adversely affect the health of these crabs. In this study, we evaluated the underlying response mechanism of E. sinensis to acute hypoxic stress by analyzing antioxidant parameters, glycolytic indicators, and hypoxia signaling factors. The crabs were exposed to hypoxia for 0, 3, 6, 12, and 24 h and reoxygenated for 1, 3, 6, 12, and 24 h. The hepatopancreas, muscle, gill, and hemolymph were sampled at different exposure times to detect the biochemical parameters and gene expression. The results showed that the activity of catalase, antioxidants, and malondialdehyde in tissues significantly increased under acute hypoxia and gradually decreased during the reoxygenation phase. Under acute hypoxic stress, glycolysis indices, including hexokinase (HK), phosphofructokinase, pyruvate kinase (PK), pyruvic acid (PA), lactate dehydrogenase (LDH), lactic acid (LA), succinate dehydrogenase (SDH), glucose, and glycogen in the hepatopancreas, hemolymph, and gills increased to varying degrees but recovered to the control levels after reoxygenation. Gene expression data showed that hypoxia signaling pathway-related genes, including hypoxia-inducible factor-1α/β (HIF1α/β), prolyl hydroxylase (PHD), factor inhibiting hypoxia-inducible factor (FIH), and glycolysis-related factors (HK and PK) were upregulated, showing that the HIF signaling pathway was activated under hypoxic conditions. In conclusion, acute hypoxic exposure activated the antioxidant defense system, glycolysis, and HIF pathway to respond to adverse conditions. These data contribute to elucidating the defense and adaptive mechanisms of crustaceans to acute hypoxic stress and reoxygenation.

Chlorbenzuron caused growth arrest through interference of glycolysis and energy metabolism in Hyphantria cunea (Lepidoptera: Erebidae) larvae

Chlorbenzuron is a kind of benzoylphenylureas (BPUs), which plays a broad role in insect growth regulators (IGRs), with an inhibitory effect on chitin biosynthesis. However, BPUs how to regulate glycolysis and insect growth remains largely unclear. Here, we investigated the effects of chlorbenzuron on growth, nutritional indices, glycolysis, and carbohydrate homeostasis in Hyphantria cunea, a destructive and highly polyphagous forest pest, to elucidate the action mechanism of chlorbenzuron from the perspective of energy metabolism. The results showed that chlorbenzuron dramatically restrained the growth and nutritional indices of H. cunea larvae and resulted in lethality. Meanwhile, we confirmed that chlorbenzuron significantly decreased carbohydrate levels, adenosine triphosphate (ATP), and pyruvic acid (PA) in H. cunea larvae. Further studies indicated that chlorbenzuron caused a significant enhancement in the enzyme activities and mRNA expressions of hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK), resulting in increased glycolytic flux. Expressions of genes involved in the AMP-activated protein kinase (AMPK) signaling pathway were also upregulated. Moreover, chlorbenzuron had remarkable impacts on H. cunea larvae from the perspective of metabolite enrichment, including the tricarboxylic acid (TCA) cycle and glycolysis, indicating an energy metabolism disorder in larvae. The findings provide a novel insight into the molecular mechanism by which chlorbenzuron abnormally promotes glycolysis and eventually interferes with insect growth and nutritional indices.

Quantification of 3-bromopyruvate in rat plasma by HPLC-MS/MS employing precolumn derivatization and the application to a pharmacokinetics study

A simple high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed for the determination of 3-Bromopyruvate (3-BrPA) in rat plasma for the first time. The analytes were separated on a C18 column (100×2.1mm, 1.7 μm) and a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source was applied for detection. 3-BrPA was extracted from rat plasma with protein precipitation, and then derivatized with 4-nitro-1,2-phenylenediamine (NPDA) to obtain the mass signal because 3-BrPA could not be detected in mass spectrometry. The method was fully validated according to the FDA's guidance. The method was linear over the concentration ranges of 0.5-1000.0 ng/mL for 3-BrPA. The precision and accuracy, extraction recovery, and matrix effect were within acceptable limits. The method was then applied to support the pharmacokinetics study after 3-BrPA and 3-BrPA-L-val-L-ile (a dipeptide prodrug of 3-BrPA, 3-BrPA-L-valine-L-isoleucine) had been administered to the Sprague-Dawley rats, respectively.

Evaluation of Optimal Reference Genes for qRT-PCR Analysis in Hyphantria cunea (Drury)

The relative quantification of gene expression is mainly achieved through reverse transcription-quantitative PCR (qRT-PCR); however, its reliability and precision rely on proper data normalization using one or more optimal reference genes. Hyphantria cunea (Drury) has been an invasive pest of forest trees, ornamental plants, and fruit trees in China for many years. Currently, the molecular physiological role of reference genes in H. cunea is unclear, which hinders functional gene study. Therefore, eight common reference genes, RPS26, RPL13, UBI, AK, RPS15, EIF4A, β-actin, α-tub, were selected to evaluate levels of gene expression stability when subjected to varied experimental conditions, including developmental stage and gender, different tissues, larvae reared on different hosts and different larval density. The geNorm, BestKeeper, ΔCt method, and NormFinder statistical algorithms were used to normalize gene transcription data. Furthermore, the stability/suitability of these candidates was ranked overall by RefFinder. This study provides a comprehensive evaluation of reference genes in H. cunea and could help select reference genes for other Lepidoptera species.