Academic literature on the topic 'Cecropin B'

Cecropins, originally found in insects, are a group of cationic antimicrobial peptides. Most cecropins have an amphipathic N-terminal segment and a largely hydrophobic C-terminal segment, and normally form a helix-hinge-helix structure. In this study, we developed the novel 32-residue cecropin-like peptide cecropin DH by deleting the hinge region (Alanine-Glycine-Proline) of cecropin B isolated from Chinese oak silk moth, Antheraea pernyi. Cecropin DH possesses effective antibacterial activity, particularly against Gram-negative bacteria, with very low cytotoxicity against mammalian cells. Interactions between cecropin DH and the highly anionic lipopolysaccharide (LPS) component of the Gram-negative bacterial outer membrane indicate that it is capable of dissociating LPS micelles and disrupting LPS aggregates into smaller assemblies, which may play a vital role in its antimicrobial activity. Using LPS-stimulated mouse macrophage RAW264.7 cells, we found that cecropin DH exerted higher potential anti-inflammatory activity than cecropin B, as demonstrated by the inhibition of pro-inflammatory cytokines nitric oxide production and secretion of tumor necrosis factor-α. In conclusion, cecropin DH has potential as a therapeutic agent for both antibacterial and anti-inflammatory applications.

Pathogenic bacteria, such as Xanthomonas campestris pv. pruni, cause diseases of significant economical implications in the Prunus genus. Cecropins are naturally occurring bactericidal peptides found in the hemolymph of insects. Cecropins cause channel formation in membranes and lysis of bacterial cells. We are interested in engineering the gene for cecropin into peach (Prunus persica) and other fruit tree species. The objective of this study was to determine the effect of cecropin B on viability, using fluorescein diacetate staining, and on changes in transmembrane electrical potential (PD) using the fluorescing probe merocyanine-540. Protoplasts were isolated from shoot-tip cultures in a CPW13M (salts + 0.71M mannitol) solution containing 2% cellulase and 0.5% macerase, while cells were isolated in CPW15.4S (salts + 0.45M sucrose) containing 0.5% cellulase and 0.5% macerase. Cecropin B (1μM) had no effect on viability and changes in PD, while 10μM had a slight effect, and 100μM cecropin B caused significant depolarization and lysis of peach protoplasts. No effect on viability and change in PD were observed in cells when treated with 1-100μM cecropin B. These results suggest that cells and protoplasts of peach can resist cecropin B in the concentration range that causes lysis of plant pathogenic bacteria. The implication of using cecropin to increase microbial disease resistance will be discussed.

ABSTRACT Cecropin B is a cationic antimicrobial peptide originally isolated from the diapausing pupae of the giant silk moth, Hylphora cecropia. Cecropin B elicits its antimicrobial effects through disruption of the anionic cell membranes of gram-negative bacteria. Previous work by our laboratory demonstrated that a constitutively expressed cecropin B transgene conferred enhanced resistance to bacterial infection in medaka. The development of antibiotic resistance by pathogenic bacteria is a growing problem. The potential for fish bacterial pathogens to develop resistance to cecropin B was addressed in this study. Four fish bacterial pathogens were selected for the study based on their importance in aquaculture. Vibrio anguillarum, Vibrio vulnificus, and Yersinia ruckeri all exhibited inducible resistance to cecropin B. The inducible resistance of these three pathogens was correlated with reversible changes in their ultrastructures, as observed by scanning electron microscopy. V. anguillarum was demonstrated to become more adhesive to a CHSE-214 cell monolayer and to cause increased cumulative mortality in medaka following exposure to cecropin B. This work demonstrates that the resistance of fish bacterial pathogens to cecropin B is inducible and suggests that resistance to other cationic antimicrobial peptides may occur through similar means. The observed changes in ultrastructure and infectivity suggest that resistance to antimicrobial peptides is an integral part of the pathogenesis of fish gram-negative bacterial pathogens.

Background and aims: Antimicrobial peptides constitute a family of bioactive peptides that are involved in the body defense. Recently, their anti-cancer properties, especially by inducing apoptosis, have been proven in in vitro studies. Therefore, in this study, the effects of cecropin B as an antimicrobial peptide on breast cancer growth, hematological parameters, and histopathological changes in rats were evaluated. Methods: Twenty-four female rats were randomly divided into 4 groups. The cancer group, control group, cecropin B group, and cancer group treated with cecropin B. The tumor size was measured at the beginning and the completion of the treatment period. Blood samples were collected for assessment of the hematological parameters and Bax and Bcl2 levels. Tumor tissues were removed for histopathological analysis. Results: The tumor size had a significant increase in the cancer group and cancer group treated with cecropin at the end of the treatment. A significant decrease in mean cell volume, white blood cell count and Bcl2 level and a significant increase in hemoglobin and Bax levels were observed in the cancer group treated with cecropin B compared to cancer group. Changes in other parameters were not significant. Histopathological study showed the invasion of mitotic cells to stromal and muscular tissues of the breast in the cancer group, while focal destruction of tissue and cell death were observed in the cancer group treated with cecropin B. Conclusion: The results showed that cecropin B has been able to reduce tumor growth and have little side effects on hematologic factors probably through apoptosis.

We examined the susceptibilities of Bordetella pertussis strains to several antimicrobial peptides by determining the concentration required to inhibit or kill 50% of the bacterial population. The peptides are ranked in decreasing potency as follows: cecropin B > cecropin A > melittin > cecropin P1 > (ala8,13,18)-magainin II amide > mastoparan = defensin HNP1 > protamine > or = magainin II = magainin I. By using a radial diffusion assay to compare susceptibilities between strains, wild-type B. pertussis BP338 was more resistant than the avirulent bvg mutant strain BP347 and the brk mutant strain BPM2041 to killing by cecropin P1. In contrast, compared with the wild type, the avirulent BP347 strain was highly resistant to killing by protamine and defensin HNP1.

碩士
國立陽明大學
熱帶醫學研究所
95
Cecropins have been demonstrated to function as bactericidal peptides in insects. A few cecropin cDNAs were isolated and investigated in various mosquitoes. In this study, expression profiles of three cecropin cDNAs (A, B, and E) were characterized extensively in Aedes aegypti. Among them, a novel A. aegypti cecropin E (AaCecE) was verified to the first time. In vivo system, AaCecA and E were found to be inducible after bacterial challenge, but AaCecB was constitutively expressed. A specific polyclonal antibody against AaCecE was generated. AaCecE was verified to be secreted into hemolymph in vivo and in vitro, and it was proved to associate with bacteria after co-incubation. Three cecropin gene sequences (AaCecA/B/E) were fetched from genomic database of A. aegypti. The diverse promoter regions of them were constructed to the upstream of a red fluorescent reporter gene and transfected into C6/36 cells. The AaCecE promoter revealed an inducible characteristic after bacterial challenge, but the induction of AaCecA promoter by bacteria was not as significant as that of AaCecE. Deletion analysis of AaCecA promoter was not corresponding to any expected elements. However, deletions to remove the region from -1,445 bp to -693 bp of the AaCecE promoter dramatically eliminated the inducible function indicating that a transcription factor containing homeodomain, POU might be important for induction of AaCecE expression. This study provides better understanding of A. aegypti cecropin from mRNA, protein to gene levels. Moreover, this reporter system will be a powerful tool for signal transduction study related to mosquito immune regulations.

博士
國立清華大學
生命科學系
95
Cecropin B (CB) is a 35-residue natural antimicrobial peptide isolated from the immune hemolymph of Hyalophora cecropia. CB shows a broad spectrum of activity against bacteria but has little cytolytic effect. CD measurements revealed that CB adopts random structure in aqueous solution but form helical conformation in polar solvent. The solution structure of CB in 20% HFIP was studied by using NMR spectroscopy. It consists of two amphipathic alpha-helices (residues 4-21 and 25-34) connected by a proline kink region (residues 22-24). In order to undertake the structural dissection of CB, CB-N27 (residues 1-27) and CB-C17 (residues 19-35) were synthesized to investigate the membrane permeabilities, fusogenic effect, and antimicrobial activities. The MIC test the two truncated form of CB both loss its antibacterial activity, suggesting the adequate peptide length of the CB is required in its antimicrobial function. CB1 was constructed by replacing the C-terminal segment with N-terminal sequence of CB, the polycationic property of CB1 make it restored the antimicrobial activity. The N-terminal polycationic and amphipathic sequence may contribute to antimicrobial activity. Furthermore CB-N27 and CB-C17 both inhibited membrane lysis, lipid mixing, and antibacterial activity. Suggesting that the optimal length of N-terminal positively charged residues and C-terminal hydrophobic segment are critical factors for its functions. The helix-hinge-helix structure of CB provides the flexibility for its two ��-helices and facilitates the interactions to lipid membrane. Several natural antimicrobial peptides including cecropins, magainins and melittins have been found to kill cancer cells. However, their efficacy may not be adequate for their development as anticancer agents. In this study, we used a natural antimicrobial peptide, cecropin B (CB), as a template to generate a novel anticancer peptide. The consensus pattern of cecropins is W-x(0,2)-[KDN]-x-{L}-K-[KRE]-[LI]-E-[RKN] (PROSITE: PS00268), and this signature sequence is located at N-terminus of CB. CB1a was constructed by repeating the signature sequence of CB three times and including a hinge near C-terminus. The circular dichroism spectra show that CB1a is unstructured in aqueous solution, but adopt a helical conformation in membrane-like environment. The solution structure of CB1a in polar solvent was also studied by NMR. CB1a formed a helix-hinge-helix in 20 % HFIP solution, and the bent angle between two helical segments was ranging from 60° to 110°. A heparin-binding motif is located in the central part of helix 1. Isothermal titration calorimetry reveals the association constant of CB1a bound to low molecular weight heparin is 1.66×105 M-1 at physiological ionic strength at 25°C. Binding of CB1a to heparin produces a large conformational change toward a more structural state. CB1a demonstrated promising activity against several cancer cells with low toxicity to the non-cancer cells. The IC50 of CB1a on leukemia and stomach carcinoma cells were in the range of 2- to 8-fold lower than those of CB. Besides, CB1a displayed low hemolytic property on human red blood cell. These properties might make CB1a a good candidate for use as an anticancer agent.

博士
國立陽明大學
微生物及免疫學研究所
106
Most of antimicrobial peptides (AMPs) can be induced rapidly and provide a non-specific killing of invading microbes. However, some of AMPs with no or low induced expression during the invasion of pathogens have weak antimicrobial activity. We hypothesized that those AMPs with no or low induced expression may play important roles in other physiological functions. Subsequently, we analysed the expression profiles of 10 cecropins in bacteria-inoculated Aedes aegypti and found Aedes aegypti cecropin B (Aacec B) was uninduced by bacterial challenges in adults and was expressed constitutively in pupae. Knockdown in the pupae of Aacec B using double-stranded RNA (dsRNA) resulted in high mortality, the emergence of deformed adults and an impairment of pharate adult cuticle formation with fewer lamellae being deposited and the helicoidal pattern of the chitin microfibrils being disorganized. Simultaneous injection of Aacec B dsRNA and Aacec B peptide into pupae significantly reduced this mortality and no deformed adults then emerged. The expression levels of Ae. aegypti prophenoloxidase (AaPPO) 3 and AaPPO 4 were significantly reduced in the Aacec B knockdown pupae. Exogenous Aacec B peptide significantly enhanced the transcription of AaPPO 3 in pupae. Knockdown of AaPPO 3 in pupae caused effects similar to Aacec B-knockdown. The Aacec B peptide could be detected in both the cytoplasm and nuclei of pupal cells and was able to bind to the TTGG(A/C)A motif in AaPPO 3 DNA both in vitro and in vivo. These findings suggest that Aacec B plays a crucial role in pharate adult cuticle formation via the regulation of AaPPO 3 gene expression in pupae.