title: Cellular internalization and cytotoxicity of the antimicrobial proline-rich peptide Bac7(1-35) in monocytes/macrophages, and its activity against phagocytosed Salmonella typhimurium.
abstract: Bac7(1-35) is an active fragment of the bovine cathelicidin antimicrobial peptide Bac7, which selectively inactivates Gram-negative bacteria both in vitro and in mice infected with Salmonella typhimurium. It has a non-lytic mechanism of action, is rapidly internalized by susceptible bacteria and mammalian cells and likely acts by binding to internal targets. In this study we show that Bac7(1-35) accumulates selectively within primed macrophages with respect to resting monocytes. Confocal microscopy analysis showed that the peptide mainly distributes in the cytoplasm and perinuclear region of macrophages within 3 hours of incubation, without affecting cell viability. Cytotoxicity studies showed that the peptide does not induce necrotic or apoptotic damage up to concentrations 50-100-fold higher than minimal inhibitory concentrations (MIC). Moreover, Bac7(1-35) did not affect the ability of macrophages to engulf S. typhimurium, a species that may proliferate within this cell type. Conversely, when added to macrophages after phagocytosis, Bac7(1-35) caused a significant reduction in the number of recovered bacteria, indicating that it can kill the engulfed microorganisms directly and/or indirectly, via activation of the defense response of the cells.
authors.forename: Chiara
authors.initials: C
authors.lastname: Pelillo
authors.forename: Monica
authors.initials: M
authors.lastname: Benincasa
authors.forename: Marco
authors.initials: M
authors.lastname: Scocchi
authors.forename: Renato
authors.initials: R
authors.lastname: Gennaro
authors.forename: Alessandro
authors.initials: A
authors.lastname: Tossi
authors.affiliation: Dept. of Life Sciences, University of Trieste, Via Giorgieri 5 - 34127 Italy. pacorsab@units.it.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pacor
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000493:pharmacokinetics* / Q000494:pharmacology*; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D010456:Peptides, Cyclic / Q000493:pharmacokinetics* / Q000494:pharmacology; D010587:Phagocytosis; D012480:Salmonella Infections / Q000188:drug therapy*; D012486:Salmonella typhimurium / Q000187:drug effects*
chemical_list: D000890:Anti-Infective Agents; D010456:Peptides, Cyclic; C056454:bactenecin