Bicyclic Peptide Based Lectinomimic

Peptide based lectin mimetics represent an attractive approach for the development of artificial carbohydrate receptors that might find application in bio-analytical and medicinal fields. Taking into consideration the structure of typical lectin binding site, we have designed a novel artificial receptor molecule possessing a rigid three-dimensional structure, hydrogen-bonding site and lipophilic binding pocket to promote hydrophobic interaction and hydrogen-bonding. A new solid- phase synthetic approach that allows complete synthesis of desired bicyclic peptide 1 on the solid support was developed. CD spectra of peptides 1 and 2 indicate that the structure of 1 is rather rigid and preorganised for the three-dimensional monosaccharide substrates binding. The binding affinities of bicyclic peptide receptor 1 toward various carbohydrate substrates at physiologically relevant conditions were estimated by UV/vis and fluorimetric titration experiments, and the observed values are in the millimolar range. With these results we have demonstrated that the bicyclic peptide 1 represent a promising basis for the design of new and more efficient carbohydrate receptors that may have broader application in bio-analytical or medicinal field

Cyclic Lipodepsipeptides in Novel Antimicrobial Drug Discovery

Naturally occurring cyclic depsipeptides, microbial secondary metabolites that contain one or more ester bonds in addition to the amide bonds, have emerged as an important source of pharmacologically active compounds or promising lead structures for the development of novel synthetically derived drugs. In particular, their lipidated derivatives have shown the greatest therapeutic potential as antimicrobial agents. Some of those compounds are either already marketed (daptomycin 37) or in advanced stages of clinical development (ramoplanin 32) for the treatment of complicated infections caused by multidrug- resistant bacterial strains. As bacteria progressively become resistant to frontline antimicrobial agents, our capacity to effectively treat bacterial infections becomes severely hindered. Therefore, identifying novel antibacterial targets and new antibacterial chemotherapeutics capable of treating infections from drug-resistant microorganisms is of vital importance.(doi: 10.5562/cca1819

Microenvironment Influence of a Novel Bioengineered Wound Product, APIS®: A Preliminary In Vitro Analysis of Inflammatory Marker and Growth Factor Secretion

Objective. Preliminary biological activity assessment of a novel bioengineered wound product (APIS®, SweetBio, Inc., Memphis, TN, USA), a synthesis of gelatin, Manuka honey, and hydroxyapatite, with in vitro indications to protect, instill balance to, and progress the wound microenvironment. Approach. The biological activity the bioengineered wound product (BWP) elicits on human cells in vitro was assessed by evaluating matrix metalloproteinase- (MMP-) related proteins expressed by macrophages and secretion of growth factors in fibroblasts. Cells were cultured with no treatment, stimulated with lipopolysaccharides (LPS), or seeded directly on the BWP for 24 hours. An additional 72-hour time point for the BWP was assessed to determine if the BWP maintained its activity compared to itself at 24 hours. Cell culture supernatants were assayed to quantify secreted protein levels. Results. MMP-9 secretion from macrophages seeded on the BWP were nondetectable (P<0.01), while a tissue inhibitor of MMP (TIMP-1) was detected. This decreased the overall MMP-9/TIMP-1 ratio secreted from macrophages seeded on the BWP compared to the controls. Additionally, the secretion of prohealing growth factors such as basic fibroblast growth factor (FGFb) and vascular endothelial growth factor (VEGF) was observed. Conclusion. Results from this preliminary in vitro evaluation suggest that the BWP has the potential to instill balance to the wound microenvironment by reducing the MMP-9/TIMP-1 ratio secretion from macrophages and progress previously stalled chronic wounds towards healing by triggering the release of growth factors from fibroblasts

In vitro and in vivo activities of novel cyclic lipopeptides against staphylococcal biofilms

A worldwide public health problem has resulted from the alarming spread of multi-drug resistant bacteria combined with the frequent occurrence of biofilm-type infections, creating a growing need for new therapies. In this study, we have demonstrated that novel cyclic lipopeptides, such as 1, cyclo-[D-Ala-(12-guanidinododecanoyl)Thr-D-Val-Val-DaThr-D-Asn], and 2, cyclo-[D-Ala-(12-guanidinododecanoyl)Dap-D-Val-Val-D-aThr-D-Asn], derived from the fusaricidin/ LI-F natural products efficiently inhibit the growth of Staphylococcus aureus biofilm in vitro at their minimum inhibitory concentrations (MICs). Complete S. aureus biofilm eradication was observed at 3 x MIC for 1 and 4 x MIC for 2. Promising in vivo activity was demonstrated by the ability of depsipeptide 1 to reduce the proliferation of methicillinresistant S. aureus US300 in a porcine wound model. Due to their unique structure and potent antibacterial and antibiofilm activities, cyclic lipopeptides that belong to the fusaricidin/LI-F family of antibiotics represent particularly attractive lead structures for the development of new antibacterial agents capable of treating complicated biofilm-associated infections

Bioinspired Strategy for the Ribosomal Synthesis of Thioether-Bridged Macrocyclic Peptides in Bacteria

Inspired by the biosynthetic logic of lanthipeptide natural products, a new methodology was developed to direct the ribosomal synthesis of macrocyclic peptides constrained by an intramolecular thioether bond. As a first step, a robust and versatile strategy was implemented to enable the cyclization of ribosomally derived peptide sequences via a chemoselective reaction between a genetically encoded cysteine and a cysteine-reactive unnatural amino acid (<i>O</i>-(2-bromoethyl)-tyrosine). Combination of this approach with intein-catalyzed protein splicing furnished an efficient route to achieve the spontaneous, post-translational formation of structurally diverse macrocyclic peptides in bacterial cells. The present peptide cyclization strategy was also found to be amenable to integration with split intein-mediated circular ligation, resulting in the intracellular synthesis of conformationally constrained peptides featuring a bicyclic architecture

Identification of Novel Cyclic Lipopeptides from a Positional Scanning Combinatorial Library with Enhanced Antibacterial and Antibiofilm Activities

Treating bacterial infections can be difficult due to innate or acquired resistance mechanisms, and the formation of biofilms. Cyclic lipopeptides derived from fusaricidin/LI-F natural products represent particularly attractive candidates for the development of new antibacterial and antibiofilm agents, with the potential to meet the challenge of bacterial resistance to antibiotics. A positional-scanning combinatorial approach was used to identify the amino acid residues responsible for driving antibacterial activity, and increase the potency of these cyclic lipopeptides. Screening against the antibiotic resistant ESKAPE pathogens revealed the importance of hydrophobic as well as positively charged amino acid residues for activity of this class of peptides. The improvement in potency was especially evident against bacterial biofilms, since the lead cyclic lipopeptide showed promising in vitro and in vivo anti-biofilm activity at the concentration far below its respective MICs. Importantly, structural changes resulting in a more hydrophobic and positively charged analog did not lead to an increase in toxicity toward human cells

Identification of Novel Cyclic Lipopeptides from a Positional Scanning Combinatorial Library with Enhanced Antibacterial and Antibiofilm Activities

Treating bacterial infections can be difficult due to innate or acquired resistance mechanisms, and the formation of biofilms. Cyclic lipopeptides derived from fusaricidin/LI-F natural products represent particularly attractive candidates for the development of new antibacterial and antibiofilm agents, with the potential to meet the challenge of bacterial resistance to antibiotics. A positional-scanning combinatorial approach was used to identify the amino acid residues responsible for driving antibacterial activity, and increase the potency of these cyclic lipopeptides. Screening against the antibiotic resistant ESKAPE pathogens revealed the importance of hydrophobic as well as positively charged amino acid residues for activity of this class of peptides. The improvement in potency was especially evident against bacterial biofilms, since the lead cyclic lipopeptide showed promising in vitro and in vivo anti-biofilm activity at the concentration far below its respective MICs. Importantly, structural changes resulting in a more hydrophobic and positively charged analog did not lead to an increase in toxicity toward human cells