DNA Topoisomerase 1 Structure-BASED Design, Synthesis, Activity Evaluation and Molecular Simulations Study of New 7-Amide Camptothecin Derivatives Against Spodoptera frugiperda

Chemical Proteomics Reveals That Camptothecin Weakens Insect Immunity against Bacteria by Suppressing Antimicrobial Peptide Expression

Plant natural products are crucial in defending against herbivorous insects and are widely used in pest control, yet their mechanisms remain complex and insufficiently studied. This study employed a reverse strategy to investigate the mechanism of camptothecin (CPT), a botanical pesticide. By using a CPT-based chemical probe coupled with proteomic analysis, immune-related proteins, including those involved in prophenoloxidase (PPO) activation and antimicrobial peptide (AMP) synthesis, were identified in the Asian corn borer, Ostrinia furnacalis. The findings demonstrated that CPT weakens insect immunity, primarily by inhibiting AMP synthesis rather than affecting PPO activation. Specifically, CPT downregulated the expression of genes in the IMD pathway and those encoding AMPs (attacin and gloverin). Additionally, CPT-fed insects exhibited reduced antibacterial activity. This research uncovers a novel mechanism of CPT as an insect immunosuppressant, offering new insights that may enhance the application of CPT in pest control.

Design, Synthesis, and Biological Evaluation of Pyrido [1,2-α] Pyrimidinone Mesoionic Derivatives Bearing Propenylbenzene as the Vector Control Insecticide

A series of novel pyrido [1,2-α] pyrimidinone mesoionic derivatives bearing a propenylbenzene group at the 1-position were synthesized on the basis of the structure of mesoionic insecticides triflumezopyrim and dicloromezotiaz via a rationally conceived pharmacophore model and evaluated for their insecticidal activities against three insect vectors. The bioassay results showed that some compounds exerted remarkable insecticidal activities against M. domestica, Ae. albopictus, and B. germanica. Particularly, compound 26l displayed outstanding insecticidal activity against Ae. Albopictus, with an LC50 value of 0.45 μg/mL, far superior to that of imidacloprid (LC50 = 1.82 μg/mL) and equivalent to that of triflumezopyrim (0.35 μg/mL). Meanwhile, compound 34l presented a broad insecticidal spectrum, with LC50 values of 1.51 μg/g sugar, 0.52 μg/mL and 0.14 μg/adult, which were about 2.88, 3.50, and 1.50 times better than that of imidacloprid (LC50 = 4.35 μg/g sugar, 1.82 μg/mL and 0.21 μg/adult against M. domestica, Ae. albopictus, and B. germanica, respectively) and equivalent to that of triflumezopyrim against M. domestica (1.13 μg/g sugar) and Ae. albopictus (0.35 μg/mL) but lower than the potency against B. germanica (0.06 μg/g sugar). The molecular docking study by energy minimizations revealed that introducing propenylbenzene at the 1-position of compounds 26l and 34l could embed into the binding pocket of nicotinic acetylcholine receptors and form pi-alkyl interaction with LEU306. These results demonstrated that compounds 26l and 34l could be promising candidates for vector control insecticides, which deserved further investigation.

Camptothecin-based prodrug nanomedicines for cancer therapy

Camptothecin (CPT) is a cytotoxic alkaloid that attenuates the replication of cancer cells via blocking DNA topoisomerase 1. Despite its encouraging and wide-spectrum antitumour activity, its application is significantly restricted owing to its instability, low solubility, significant toxicity, and acquired tumour cell resistance. This has resulted in the development of many CPT-based therapeutic agents, especially CPT-based nanomedicines, with improved pharmacokinetic and pharmacodynamic profiles. Specifically, smart CPT-based prodrug nanomedicines with stimuli-responsive release capacity have been extensively explored owing to the advantages such as high drug loading, improved stability, and decreased potential toxicity caused by the carrier materials in comparison with normal nanodrugs and traditional delivery systems. In this review, the potential strategies and applications of CPT-based nanoprodrugs for enhanced CPT delivery toward cancer cells are summarized. We appraise in detail the chemical structures and release mechanisms of these nanoprodrugs and guide materials chemists to develop more powerful nanomedicines that have real clinical therapeutic capacities.

The recent developments of camptothecin and its derivatives as potential anti-tumor agents

This review article focuses on the research progress made in the structural modifications of camptothecin (CPT), a potent cytotoxic natural alkaloid. CPT possesses a unique 5-fused ring structure and exhibits various beneficial activities such as anti-proliferative, anti-fungal, insecticidal, and anti-SARS-CoV-2 properties. CPT and its analogs, including Topotecan and Irinotecan, have been successfully developed and marketed as topoisomerase I inhibitors. To enhance the therapeutic potential of CPT, researchers have undertaken structural modifications primarily on the A, B, and E rings of the CPT core structure. These modifications aim to improve the efficacy, selectivity, and pharmacokinetic properties of CPT derivatives. The article reviews the advancements in hybridizing CPT with other bioactive compounds, the synthesis of novel CPT analogs, and their associated biological activities. Moreover, the structure-activity relationship (SAR) of these modified CPT derivatives is summarized to gain insights into their structure-function correlations. In addition to discussing the modifications and biological activities of CPT derivatives, the article also touches upon the mechanism of parent drug release. Many CPT derivatives are prodrugs, meaning they require metabolic activation to generate the active form of the drug. It is a resource for researchers interested in developing novel anti-tumor agents based on CPT, addressing the limitations associated with the parent drug, and exploring various aspects of CPT modifications.

Chitinase is a Potent Insecticidal Molecular Target of Camptothecin and Its Derivatives

Camptothecin (CPT) is a prominent molecule in natural product research because of its application prospects in medicine and agriculture. In this study, CPT and its derivatives were discovered to be competitive inhibitors of group II and group h insect chitinases, both of which are key components of insect chitinolytic systems. CPT and 7-ethyl-10-hydroxycamptothecin (SN-38) inhibited group II chitinase from Ostrinia furnacalis (OfChtII) with K_i values of 5.1 and 2.0 μM, respectively. Results from tryptophan fluorescence spectroscopy, molecular docking analysis, and molecular dynamics simulations revealed that both CPT and SN-38 inhibit OfChtII-C1 by interacting with solvent-exposed tryptophan residues in a substrate-binding cleft. CPT exhibited high insecticidal activity toward the orthopteran pest Locusta migratoria, possibly because of the midgut metabolism of CPT, with only moderate activities toward lepidopteran pests. Even though SN-38 exhibited much lower insecticidal activities than CPT, it still showed higher inhibitory activity toward chitinase. This study reports a new molecular target of CPT and provides insights into molecular design of CPT-based insecticides against different kinds of pests.

Group housing enhances mating and increases the sensitization of chemical cues in Bactrocera dorsalis

BACKGROUND

Changes in population density have profound impacts on mating behaviors in group-living animals. The plasticity of mating behavior enables insects to respond to social signals and adjust mating frequency in accordance with rival competition and reproductive opportunity.

RESULTS

In this study, we found that low levels of cis-vaccenyl acetate (cVA), a Drosophila pheromone, increased mating rates of Bactrocera dorsalis, but high concentrations of cVA inhibited mating, indicating a functional role of cVA in regulating mating behaviors in insect species other than Drosophila. Moreover, we demonstrated that group housing conditions had positive effects for B. dorsalis on their mating rates, responses toward cVA and cVA-mediated mating behaviors, which are dependent on the activity of c-AMP reponse element binding protein (CREB) binding protein (CBP).

CONCLUSIONS

Our data suggest that CBP-mediated plasticity in mating behavior and chemical recognition enables insects to adapt to different housing conditions and highlight the potential of cVA as an efficient agent in regulating mating behaviors in insect species other than Drosophila. © 2022 Society of Chemical Industry.

The Potential Binding Interaction and Hydrolytic Mechanism of Carbaryl with the Novel Esterase PchA in Pseudomonas sp. PS21

Microbial bioremediation is a very potent and eco-friendly approach to alleviate pesticide pollution in agricultural ecosystems, and hydrolase is an effective element for contaminant degradation. In the present study, a novel Mn²⁺-dependent esterase, PchA, that efficiently hydrolyzes carbamate pesticides with aromatic structures was identified from Pseudomonas sp. PS21. The hydrolytic activity was confirmed to be related closely to the core catalytic domain, which consists of six residues. The crucial residues indirectly stabilized the position of carbaryl via chelating Mn²⁺ according to the binding model clarified by molecular simulations, and the additional hydrophobic interactions between carbaryl with several hydrophobic residues also stabilized the binding conformation. The residue Glu398, by serving as the general base, might activate a water molecule and facilitate PchA catalysis. This work offers valuable insights into the binding interaction and hydrolytic mechanism of carbaryl with the hydrolase PchA and will be crucial to designing strategies leading to the protein variants that are capable of degrading related contaminants.

Effects of camptothecin on histological structures and gene expression profiles of fat bodies in Spodoptera frugiperda

Spodoptera frugiperda is a serious threat to global food production. Our previous study demonstrated that Camptothecin (CPT), a bioactive secondary metabolite from Camptotheca acuminata (Decne: Nyssaceae), exhibits adverse impact on the larval midgut of S. frugiperda and inhibits insect growth. However, effects of CPT on fat bodies of S. frugiperda larvae have not been examined yet. In the present study, we found that histological structures of fat bodies of S. frugiperda larvae were damaged in insects treated with CPT. Comparative transcriptomic analyses among different fat body samples from controls and insects treated with 1.0 and 5.0 μg/g CPT were performed. A total of 4212 and 5044 differentially expressed genes (DEGs) were identified in the samples treated with 1.0 and 5.0 μg/g CPT, respectively. Our data indicated that the pathways of detoxification, immune response, fatty acids, chitin, and hormone biosynthesis in fat bodies were affected by CPT treatments based on DEGs. These results provided a comprehensive view of the damage and gene expression changes in fat bodies of S. frugiperda after CPT exposure, which shall be useful to reveal the mechanism of CPT toxicity against S. frugiperda in future.

Plant-microbe interactions implicated in the production of camptothecin - An anticancer biometabolite from Phyllosticta elongata MH458897 a novel endophytic strain isolated from medicinal plant of Western Ghats of India

Endophytic wild fungal strain Phyllosticta elongata MH458897 isolated from medicinal plant Cipadessa baccifera from the Western Ghats region of Sathyamangalam Tiger Reserve Forest. This endophytic fungus has potential of effective anticancer drug Camptothecin (CPT). Endophytic fungi act as key symbionts in-between plants and ecosystem in the biosphere. This recently identified microbial population inside the plants produces many defence metabolites against plant pathogens. Among these defense metabolites, CPT gained much attention because of its effective anticancer activity. The maximum yield of CPT produced by optimizing the various factors like DEKM07 medium, pH 5.6, incubation time using Response Surface Methodology based on Central Composite Design. Extracted CPT is characterized using High Performance Liquid Chromatography and Electrospray ionization-Mass spectrometry. The highest yield of CPT was 0.747 mg/L was produced at optimized factors of dextrose - 50 g L^-1, peptone - 5.708 g L^-1, magnesium sulphate - 0.593 g L^-1, and incubation time - 14 days. In-vitro MTT assay revealed the CPT derivatives were cytotoxic to A-549 cancer cell line (IC₅₀ 58.28 μg/ml) as nearly compared to the (IC₅₀ 51.08 μg/ml) standard CPT. CPT producing strain P. elongata from C. baccifera has the potential of CPT biosynthesis, and could be an effective anticancer bio metabolite. This compound has been described in the literature to be an effective anticancer metabolite. Our findings support the novel lifesaving anticancer drug from endophytic fungus in forest ecosystem concludes effective utilization of key symbionts will safeguard the humans and forest ecosystem.

Camptothecin's journey from discovery to WHO Essential Medicine: Fifty years of promise

Nature represents a rich source of compounds used for the treatment of many diseases. Camptothecin (CPT), isolated from the bark of Camptotheca acuminata, is a cytotoxic alkaloid that attenuates cancer cell replication by inhibiting DNA topoisomerase 1. Despite its promising and wide spectrum antiproliferative activity, its use is limited due to low solubility, instability, acquired tumour cell resistance, and remarkable toxicity. This has led to the development of numerous CPT analogues with improved pharmacodynamic and pharmacokinetic profiles. Three natural product-inspired drugs, namely, topotecan, irinotecan, and belotecan, are clinically approved and prescribed drugs for the treatment of several types of cancer, whereas other derivatives are in clinical trials. In this review, which covers literature from 2015 to 2020, we aim to provide a comprehensive overview and describe efforts that led to the development of a variety of CPT analogues. These efforts have led to the discovery of potent, first-in-class chemotherapeutic agents inspired by CPT. In addition, the mechanism of action, SAR studies, and recent advances of novel CPT drug delivery systems and antibody drug conjugates are discussed.

Covalent Complex of DNA and Bacterial Topoisomerase: Implications in Antibacterial Drug Development

A topoisomerase-DNA transient covalent complex can be a druggable target for novel topoisomerase poison inhibitors that represent a new class of antibacterial or anticancer drugs. Herein, we have investigated molecular features of the functionally important Escherichia coli topoisomerase I (EctopoI)-DNA covalent complex (EctopoIcc) for molecular simulations, which is very useful in the development of new antibacterial drugs. To demonstrate the usefulness of our approach, we used a model small molecule (SM), NSC76027, obtained from virtual screening. We examined the direct binding of NSC76027 to EctopoI as well as inhibition of EctopoI relaxation activity of this SM via experimental techniques. We then performed molecular dynamics (MD) simulations to investigate the dynamics and stability of EctopoIcc and EctopoI-NSC76027-DNA ternary complex. Our simulation results show that NSC76027 forms a stable ternary complex with EctopoIcc. EctopoI investigated here also serves as a model system for investigating a complex of topoisomerase and DNA in which DNA is covalently attached to the protein.

Discovery of luotonin A analogues as potent fungicides and insecticides: Design, synthesis and biological evaluation inspired by natural alkaloid

The prevention and control of plant diseases and insect pests is the most crucial issue facing crop protection. To discover novel pesticide candidates with diverse chemical structures from natural products, a series of luotonin A analogues were designed, synthesized and evaluated for their antifungal and insecticidal activities. Most of these compounds exhibited potent activity against Botrytis cinerea, Magnaporthe oryzae and Aphis craccivora. Among them, the antifungal activity of compound 10s against B. cinerea was comparable to azoxystrobin (EC₅₀ = 0.09 mM) and against M. oryzae (EC₅₀ = 0.19 mM) was slightly weaker than that of azoxystrobin (EC₅₀ = 0.17 mM). Compounds 10k and 10o are the most active compounds against A. craccivora having identical mortality value of 42.05% at 50 μg/mL, respectively, which were slightly lower than pymetrozine (51.14%) at the same concentration. Revealed morphological changes of the fungal cell surface by scanning electron microscopy indicated that luotonin A analogues might exert their antifungal activity by destroying fungal cell membrane and cell wall. Furthermore, the results of the in vivo protective and curative activities of the compound 10s against S. sclerotiorum and B. cinerea showed that the curative effect was stronger than its protective effect and the curative effects reached 67.17% and 73.82% at 80 μg/mL respectively. The above results further demonstrated the potential of luotonin A analogues as novel fungicides and insecticides.

Host AAA+ ATPase TER94 Plays Critical Roles in Building the Baculovirus Viral Replication Factory and Virion Morphogenesis

TER94 is a multifunctional AAA+ ATPase crucial for diverse cellular processes, especially protein quality control and chromatin dynamics in eukaryotic organisms. Many viruses, including coronavirus, herpesvirus, and retrovirus, coopt host cellular TER94 for optimal viral invasion and replication. Previous proteomics analysis identified the association of TER94 with the budded virions (BVs) of baculovirus, an enveloped insect large DNA virus. Here, the role of TER94 in the prototypic baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) life cycle was investigated. In virus-infected cells, TER94 accumulated in virogenic stroma (VS) at the early stage of infection and subsequently partially rearranged in the ring zone region. In the virions, TER94 was associated with the nucleocapsids of both BV and occlusion-derived virus (ODV). Inhibition of TER94 ATPase activity significantly reduced viral DNA replication and BV production. Electron/immunoelectron microscopy revealed that inhibition of TER94 resulted in the trapping of nucleocapsids within cytoplasmic vacuoles at the nuclear periphery for BV formation and blockage of ODV envelopment at a premature stage within infected nuclei, which appeared highly consistent with its pivotal function in membrane biogenesis. Further analyses showed that TER94 was recruited to the VS or subnuclear structures through interaction with viral early proteins LEF3 and helicase, whereas inhibition of TER94 activity blocked the proper localization of replication-related viral proteins and morphogenesis of VS, providing an explanation for its role in viral DNA replication. Taken together, these data indicated the crucial functions of TER94 at multiple steps of the baculovirus life cycle, including genome replication, BV formation, and ODV morphogenesis.IMPORTANCE TER94 constitutes an important AAA+ ATPase that associates with diverse cellular processes, including protein quality control, membrane fusion of the Golgi apparatus and endoplasmic reticulum network, nuclear envelope reformation, and DNA replication. To date, little is known regarding the role(s) of TER94 in the baculovirus life cycle. In this study, TER94 was found to play a crucial role in multiple steps of baculovirus infection, including viral DNA replication and BV and ODV formation. Further evidence showed that the membrane fission/fusion function of TER94 is likely to be exploited by baculovirus for virion morphogenesis. Moreover, TER94 could interact with the viral early proteins LEF3 and helicase to transport and further recruit viral replication-related proteins to establish viral replication factories. This study highlights the critical roles of TER94 as an energy-supplying chaperon in the baculovirus life cycle and enriches our knowledge regarding the biological function of this important host factor.

Effects of camptothecin on the rice blast fungus Magnaporthe oryzae

Rice blast caused by Magnaporthe oryzae B. Couch is one of the most devastating diseases on rice. Camptothecin (CPT), which was primarily isolated from Camptotheca acuminata, is well-known for its anti-tumor activities, and is also developed as a potential biological pesticide. We previously investigated the anti-microbial activities of CPT against 11 fungi, 3 oomycetes, and 4 bacteria, and found that CPT was strongly effective against M. oryzae, indicating its potential as a lead for developing fungicide against rice blast. However, the anti-fungal effects of CPT on M. oryzae need further elucidation. In this study, the anti-fungal activities of CPT against M. oryzae were further investigated, which revealed that CPT was effective against M. oryzae both in vitro and in vivo. The transcriptome of M. oryzae was analyzed after CPT treatment, which showed that CPT had a strong inhibitory effect on 'translation' and 'carbohydrate metabolism/energy metabolism' of M. oryzae. Some physiology characteristics of M. oryzae were also assayed, which confirmed that CPT inhibited RNA synthesis, protein synthesis, and carbohydrate metabolism/energy metabolism of M. oryzae, and caused membrane damage. The molecular simulation result showed that CPT binds to the interface of DNA-topoisomerase I complex of M. oryzae. In conclusion, CPT is a promising lead for developing fungicide against rice blast. CPT may bind to DNA-topoisomerase I complex of M. oryzae, thus affecting 'translation' and 'carbohydrate metabolism/energy metabolism', leading to cell death.

Harmine induced apoptosis in Spodoptera frugiperda Sf9 cells by activating the endogenous apoptotic pathways and inhibiting DNA topoisomerase I activity

Harmine, a useful botanical compound, has demonstrated insecticidal activity against some pests. However, harmine's mechanism of action has not been thoroughly elucidated to date. To preliminarily explore harmine's insecticidal mechanisms, the cytotoxicity of harmine against Spodoptera frugiperda Sf9 cells was comprehensively investigated. Our results indicated that harmine induced apoptosis in Sf9 cells, as evidenced by cellular and nuclear morphological changes, DNA laddering and increases in caspase-3-like activities. In addition, activation of the mitochondrial apoptotic pathway by harmine was confirmed by the generation of ROS, opening of mitochondrial permeability transition pores (MPTPs), increase in cytosolic Ca²⁺, changes in mRNA expression levels of genes involved in the mitochondrial apoptotic pathway and increase and release of Cytochrome c. Furthermore, lysosomal membrane permeabilization, release of cathepsin L from the lysosome into the cytosol and cleavage of caspase-3 were also triggered, which indicated that lysosomes were involved in this physiological process. Moreover, the effect of harmine on DNA topoisomerase I activity was investigated by in vivo and molecular docking experiments. These data not only verified that harmine induced apoptosis via comprehensive activation of the mitochondrial and lysosomal pathways and inhibition of DNA topoisomerase I activity in Sf9 cells but also revealed a mechanism of harmine insecticidal functions for pest control.