Pathogenic fungi synergistically cooperate with Serratia marcescens to increase cockroach mortality.

The abuse of chemical insecticides has led to strong resistance in cockroaches, and biopesticides with active ingredients based on insect pathogens have good development prospects; however, their slow effect has limited their practical application, and improving their effectiveness has become an urgent problem. In this study, the interaction between Serratia marcescens and Metarhizium anisopliae enhanced their virulence against Blattella germanica and exhibited a synergistic effect. The combination of S. marcescens and M. anisopliae caused more severe tissue damage and accelerated the proliferation of the insect pathogen. The results of high-throughput sequencing demonstrated that the gut microbiota was dysbiotic, the abundance of the opportunistic pathogen Weissella cibaria increased, and entry into the hemocoel accelerated the death of the German cockroaches. In addition, the combination of these two agents strongly downregulated the expression of Imd and Akirin in the IMD pathway and ultimately inhibited the expression of antimicrobial peptides (AMPs). S. marcescens released prodigiosin to disrupted the gut homeostasis and structure, M. anisopliae released destruxin to damaged crucial organs, opportunistic pathogen Weissella cibaria overproliferated, broke the gut epithelium and entered the hemocoel, leading to the death of pests. These findings will allow us to optimize the use of insect pathogens for the management of pests and produce more effective biopesticides.

A cuticular protein, BgCPLCP1, contributes to insecticide resistance by thickening the cockroach endocuticle.

Overuse of insecticides has led to severe environmental problems. Insect cuticle, which consists mainly of chitin, proteins and a thin outer lipid layer, serves multiple functions. Its prominent role is as a physical barrier that impedes the penetration of xenobiotics, including insecticides. Blattella germanica (L.) is a major worldwide indoor pest that causes allergic disease and asthma. Extensive use of pyrethroid insecticides, including ß-cypermethrin, has selected for the rapid and independent evolution of resistance in cockroach populations on a global scale. We demonstrated that BgCPLCP1, the first CPLCP (cuticular proteins of low complexity with a highly repetitive proline-rich region) family cuticular protein in order Blattodea, contributes to insecticide penetration resistance. Silencing BgCPLCP1 resulted in 85.0 %-85.7 % and 81.0 %-82.0 % thinner cuticle (and especially thinner endocuticle) in the insecticide-susceptible (S) and ß-cypermethrin-resistant (R) strains, respectively. The thinner and more permeable cuticles resulted in 14.4 % and 20.0 % lower survival of ß-cypermethrin-treated S- and R-strain cockroaches, respectively. This study advances our understanding of cuticular penetration resistance in insects and opens opportunities for the development of new efficiently and environmentally friendly insecticides targeting the CPLCP family of cuticular proteins.

Transcriptome analysis revealed that short-term stress in Blattella germanica to ß-cypermethrin can reshape the phenotype of resistance adaptation.

Previous studies on insect resistance have primarily focused on resistance monitoring and the molecular mechanisms involved, while overlooking the process of phenotype formation induced by insecticide stress. In this study, we compared the expression profiles of a beta-cypermethrin (ß-CYP) resistant strain (R) and a susceptible strain (S) of Blattella germanica after ß-CYP induction using transcriptome sequencing. In the short-term stress experiment, we identified a total of 792 and 622 differentially expressed genes (DEGs) in the S and R strains. Additionally, 893 DEGs were identified in the long-term adaptation experiment. To validate the RNA-Seq data, we performed qRT-PCR on eleven selected DEGs, and the results were consistent with the transcriptome sequencing data. These DEGs exhibited down-regulation in the short-term stress group and up-regulation in the long-term adaptation group. Among the validated DEGs, CUO8 and Cyp4g19 were identified and subjected to knockdown using RNA interference. Subsequent insecticide bioassays revealed that the mortality rate of cockroaches treated with ß-CYP increased by 69.3% and 66.7% after silencing the CUO8 and Cyp4g19 genes (P<0.05). Furthermore, the silencing of CUO8 resulted in a significant thinning of the cuticle by 59.3% and 53.4% (P<0.05), as observed through transmission electron microscopy and eosin staining, in the S and R strains, respectively. Overall, our findings demonstrate that the phenotypic plasticity in response to short-term stress can reshape the adaptive mechanisms of genetic variation during prolonged exposure to insecticides. And the identified resistance-related genes, CUO8 and Cyp4g19, could serve as potential targets for controlling these pest populations.

Folate-Conjugated Polymer Micelles with pH-Triggered Drug Release Properties.

Folate has been applied as a targeting moiety for various anticancer drug-delivery agents to avoid non-specific attack of normal tissues as well as to increase cellular uptake at the target tumor cells. Polymer micelles made of poly[(D,L-lactide)-co-glycolide)]-poly(ethylene glycol)-folate (PLGA-PEG-FOL) was fabricated as a tumor targeting carrier for encapsulating the anticancer drug doxorubicin. To accelerate the drug release in the endosome after folate-mediated cellular uptake, pH-sensitive poly(ß-amino ester)-PEG-FOL (PAE-PEG-FOL) was added together with PLGA-PEG-FOL to form mixed micelles. The results showed that the drug release can be triggered at different pH due to the ionization of PAE. The IC(50) of PLGA-PEG-FOL micelles is 0.46 × 10(-6) M. With 20% PAE in the mixed micelles (20:80 mixed micelles), the IC(50) decreases to 0.34 × 10(-6) M, which is comparable to that of pure PAE-PEG-FOL micelles at pH 7.4. As a result of the pH sensitivity, the PAE-PEG-FOL micelles are not stable at pH 6.5 or lower, and the drug may be released from the micelles into the extracellular environment before uptake by the cells. The 20:80 mixed micelles are relatively stable at this condition. As a result, the micelles retain more drug in the micelles for a higher degree of cellular uptake by folate receptor-mediated endocytosis, and exhibit higher cytotoxicity.

Addition of TPGS to folate-conjugated polymer micelles for selective tumor targeting.

Folate-conjugated polymer micelles poly(D,L-lactide-co-glycolide)-poly(ethylene glycol)-folate (PLGA-PEG-FOL) was fabricated to encapsulate anticancer drug doxorubicin for targeting delivery to cancer cells with overexpression of folate receptors. To increase therapeutic effect, D-alpha-tocopheryl polyethylene glycol succinate (TPGS) was added during the micelles preparation. The physicochemical study showed that the mixed micelles of PLGA-PEG-FOL and TPGS formed a homogeneous population. The addition of TPGS did not result in much variation in the micellar size, surface charge, and drug encapsulation efficiency. The cellular uptake study showed that mixed micelles with TPGS had higher cellular uptake compared with the ones without TPGS to drug-resistant cancer cells. These mixed micelles also selectively increased the cytotoxicity of drug on cancer cells but exhibited minimal cytotoxic enhancement on normal fibroblasts. Furthermore, the accumulation of rhodamine study showed that the mixed micelles with TPGS increased the cellular uptake of drugs on Caco-2 cells. This indicates that TPGS in the mixed micelles may act as P-glycoprotein inhibitor to reduce drug efflux. This new formulation with TPGS may have dual functions of folate-mediated targeting and multidrug resistance inhibition and can be promising in improving the therapeutic efficacy of polymer micellar targeting delivery system.

Selectivity of folate conjugated polymer micelles against different tumor cells.

Folate or folic acid has been employed as a targeting moiety of various anticancer agents to increase their cellular uptake within target cells since folate receptors are vastly overexpressed in several human tumors. In this study, a biodegradable polymer poly(d,l-lactide-co-glycolide)-poly(ethylene glycol)-folate (PLGA-PEG-FOL) was used to form micelles for encapsulating anticancer drug doxorubicin (DOX). The drug loading content, encapsulation efficiency and in vitro release were characterized. To evaluate the targeting ability of the folate conjugated micelles, the cytotoxicity and cellular uptake of DOX-loaded micelles on three cancer cell lines with different amount of folate receptors (KB, MATB III, C6) and normal fibroblast cells (CCL-110) were compared. The cytotoxicity of PLGA-PEG-FOL micelles to cancer cells was found to be much higher than that of normal fibroblast cells, demonstrating that the folate conjugated micelles has the ability to selectively target to cancer cells. For normal cells, the cellular uptake of PLGA-PEG-FOL micelles was similar to PLGA-PEG micelles without folate conjugation, and was substantially lower than that of cancer cells. In addition, the cell cycle analysis showed that the apoptotic percentage of normal fibroblasts was substantially lower compared with the cancer cells after exposing to DOX-loaded PLGA-PEG-FOL micelles. An optimal folate amount of approximately 40-65% on the micelles was found to be able to kill cancer cells but, at the same time, to have very low effect to normal cells.