title: Characterization of dual effects induced by antimicrobial peptides: regulated cell death or membrane disruption.
abstract: BACKGROUND
  Some reports describe lysis mechanisms by antimicrobial peptides (AMPs), while others describe the activation of regulated cell death. In this study, we compare the cell death-inducing activities of four β-hairpin AMPs (gomesin, protegrin, tachyplesin and polyphemusin II) along with their linear analogs in the human erythroleukemia K562 cell line to investigate the relationship between their structure and activity.
  
  
  METHODS
  K562 cells were exposed to AMPs. Morphological and biochemistry alterations were evaluated using light microscopy, confocal microscopy and flow cytometry.
  
  
  RESULTS
  Gomesin and protegrin displayed cytotoxic properties that their linear counterparts did not. Tachyplesin and polyphemusin II and also their linear analogs induced cell death. We were able to distinguish two ways in which these AMPs induced cell death. Lower concentrations of AMPs induced controlled cell death mechanisms. Gomesin, tachyplesin and linear-tachyplesin promoted apoptosis that was characterized by annexin labeling, sensitivity to Z-VAD, and caspase-3 activation, but was also inhibited by necrostatin-1. Gomesin and protegrin induced cell death was dependent on intracellular Ca2+ mechanisms and the participation of free radicals was observed in protegrin induced cell death. Polyphemusin II and its linear analog mainly induced necrosis. Conversely, treatment with higher concentrations of AMPs primarily resulted in cell membrane disruption, but with clearly different patterns of action for each AMP tested.
  
  
  CONCLUSIONS
  Different actions by β-hairpin AMPs were observed at low concentrations and at higher concentrations despite the structure similarity.
  
  
  CONCLUSIONS
  Controlled intracellular mechanism and direct membrane disruption were clearly distinguished helping to understand the real action of AMPs in mammalian cells.
authors.affiliation: Departamento de Bioquímica, Universidade Federal de São Paulo, R. Três de Maio 100, 04044-020, São Paulo, SP, Brazil. edgar.gamero@unifesp.br
authors.forename: Edgar J
authors.initials: EJ
authors.lastname: Paredes-Gamero
authors.forename: Marta N C
authors.initials: MN
authors.lastname: Martins
authors.forename: Fábio A M
authors.initials: FA
authors.lastname: Cappabianco
authors.forename: Jaime S
authors.initials: JS
authors.lastname: Ide
authors.forename: Antonio
authors.initials: A
authors.lastname: Miranda
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects*; D006801:Humans; D020014:K562 Cells; D009336:Necrosis; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D017382:Reactive Oxygen Species; D020169:Caspases; D002118:Calcium