Antimicrobial peptide incorporated poly(2-hydroxyethyl methacrylate) hydrogels for the prevention of Staphylococcus epidermidis-associated biomaterial infections

The effectiveness of the antimicrobial peptide maximin-4, the ultrashort peptide H-Orn-Orn-Trp-Trp-NH(2) , and the lipopeptide C(12) -Orn-Orn-Trp-Trp-NH(2) in preventing adherence of pathogens to a candidate biomaterial were tested utilizing both matrix- and immersion-loaded poly(2-hydroxyethyl methacrylate) (poly(HEMA)) hydrogels. Antiadherent properties correlated to both the concentration released and the relative antimicrobial concentrations of each compound against Staphylococcus epidermidis ATCC 35984, at each time point. Immersion-loaded samples containing C(12) -Orn-Orn-Trp-Trp-NH(2) exhibited the lowest adherence profile for all peptides studied over 1, 4, and 24 h. The results outlined in this article show that antimicrobial peptides have the potential to serve as an important weapon against biomaterial associated infections. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.

Aminoarabinose is essential for lipopolysaccharide export and intrinsic antimicrobial peptide resistance in Burkholderia cenocepacia

One common mechanism of resistance against antimicrobial peptides in Gram-negative bacteria is the addition of 4-amino-4-deoxy-l-arabinose (l-Ara4N) to the lipopolysaccharide (LPS) molecule. Burkholderia cenocepacia exhibits extraordinary intrinsic resistance to antimicrobial peptides and other antibiotics. We have previously discovered that unlike other bacteria, B. cenocepacia requires l-Ara4N for viability. Here, we describe the isolation of B. cenocepacia suppressor mutants that remain viable despite the deletion of genes required for l-Ara4N synthesis and transfer to the LPS. The absence of l-Ara4N is the only structural difference in the LPS of the mutants compared with that of the parental strain. The mutants also become highly sensitive to polymyxin B and melittin, two different classes of antimicrobial peptides. The suppressor phenotype resulted from a single amino acid replacement (aspartic acid to histidine) at position 31 of LptG, a protein component of the multi-protein pathway responsible for the export of the LPS molecule from the inner to the outer membrane. We propose that l-Ara4N modification of LPS provides a molecular signature required for LPS export and proper assembly at the outer membrane of B. cenocepacia, and is the most critical determinant for the intrinsic resistance of this bacterium to antimicrobial peptides.

Extreme antimicrobial Peptide and polymyxin B resistance in the genus burkholderia

Cationic antimicrobial peptides and polymyxins are a group of naturally occurring antibiotics that can also possess immunomodulatory activities. They are considered a new source of antibiotics for treating infections by bacteria that are resistant to conventional antibiotics. Members of the genus Burkholderia, which includes various human pathogens, are inherently resistant to antimicrobial peptides. The resistance is several orders of magnitude higher than that of other Gram-negative bacteria such as Escherichia coli, Salmonella enterica, or Pseudomonas aeruginosa. This review summarizes our current understanding of antimicrobial peptide and polymyxin B resistance in the genus Burkholderia. These bacteria possess major and minor resistance mechanisms that will be described in detail. Recent studies have revealed that many other emerging Gram-negative opportunistic pathogens may also be inherently resistant to antimicrobial peptides and polymyxins and we propose that Burkholderia sp. are a model system to investigate the molecular basis of the resistance in extremely resistant bacteria. Understanding resistance in these types of bacteria will be important if antimicrobial peptides come to be used regularly for the treatment of infections by susceptible bacteria because this may lead to increased resistance in the species that are currently susceptible and may also open up new niches for opportunistic pathogens with high inherent resistance.

CoMFA and homology-based models of the glycine binding site of N-methyl-D-aspartate receptor

Homology modeling was used to build 3D models of the N-methyl-D-aspartate (NMDA) receptor glycine binding site on the basis of an X-ray structure of the water-soluble AMPA-sensitive receptor. The docking of agonists and antagonists to these models was used to reveal binding modes of ligands and to explain known structure-activity relationships. Two types of quantitative models, 3D-QSAR/CoMFA and a regression model based on docking energies, were built for antagonists (derivatives of 4-hydroxy-2-quinolone, quinoxaline-2,3-dione, and related compounds). The CoMFA steric and electrostatic maps were superimposed on the homology-based model, and a close correspondence was marked. The derived computational models have permitted the evaluation of the structural features crucial for high glycine binding site affinity and are important for the design of new ligands.

A PEPTIDE FROM THE CAUDAL NEUROSECRETORY-SYSTEM OF THE DOGFISH SCYLIORHINUS-CANICULA THAT IS STRUCTURALLY RELATED TO UROTENSIN-I

Using reversed-phase HPLC in combination with a radioimmunoassay for ovine corticotropin-releasing hormone (CRH), a peptide with CRH-like immunoreactivity was isolated in pure form from an extract of the caudal spinal cord region of the spotted dogfish, Scyliorhinus canicula. The primary structure of the peptide was established as Pro-Ala-Glu-Thr-Pro-Asn-Ser-Leu-Asp-Leu(10)-Thr-Phe-His-Leu-Leu-Arg-Glu-Met-Ile-Glu(20)-Ile-Ala-Lys-His-Glu-Asn-Gln-Gln-Met-Gln(30)-Ala-Asp-Ser-Asn-Arg-Arg-Ile-Met-Asp-Thr(40)-Ile . NH2. This amino acid sequence shows moderate structural similarity to Catostomus urotensin I (51%) and to human CRH (56%). The data provide, therefore, chemical evidence to support the conclusions of earlier immunohistochemical studies that the diffuse caudal neurosecretory system of elasmobranchs produces a peptide that is immunochemically related to teleost urotensin I peptides. However, the primary structure of urotensin I has been poorly conserved during evolution. (C) 1995 Academic Press, Inc.

The chains of the heterodimeric amphibian skin antimicrobial peptide, distinctin, are encoded by separate messenger RNAs

Using a primer to a conserved nucleotide sequence of previously-cloned skin peptides of Phyllomedusa species, two distinct cDNAs were “shotgun” cloned from a skin secretion-derived cDNA library of the frog, Phyllomedusa burmeisteri. The two ORFs separately encode chains A and B of an analog of the previously-reported heterodimeric peptide, distinctin. LC-MS/MS analysis of native versus dithiotreitol reduced crude venom, confirmed the predicted primary sequences as well as the cystine link between the two monomers. Distinctin predominantly exists in the venom as a heterodimer (A-B), neither of the constituent peptides were detected as monomer, whereas of the two possible homodimers (A-A or B-B), only B-B was detected in comparatively low quantity. In vitro dimerization of synthetic replicates of the monomers demonstrated that besides heterodimer, both homodimers are also formed in considerable amounts. Distinctin is the first example of an amphibian skin dimeric peptide that is formed by covalent linkage of two chains that are the products of different mRNAs. How this phenomenon occurs in vivo, to exclude significant homodimer formation, is unclear at present but a “favored steric state” type of interaction between chains is most likely.

Plasma concentrations of glucagon-like peptide-2 in adult patients with treated and untreated coeliac disease

Coeliac disease is a common chronic inflammatory enteropathy characterized by villous atrophy and crypt hyperplasia in the small intestine. The mechanism of the intestinal damage in coeliac disease remains unclear. Glucagon-like peptide (GLP)-2 is an enterotrophic peptide that causes crypt hyperplasia and intestinal cell proliferation. We postulate that GLP-2 may be involved in the mucosal changes found in coeliac disease.