title: Pulmonary surfactant preserves viability of alveolar type II cells exposed to polymyxin B in vitro.
abstract: BACKGROUND
  Exogenous surfactant derived from animal lungs is applied for treatment of surfactant deficiency. By means of its rapid spreading properties, it could transport pharmaceutical agents to the terminal air spaces. The antimicrobial peptide Polymyxin B (PxB) is used as a topical antibiotic for inhalation therapy. Whereas it has been shown that PxB mixed with surfactant is not inhibiting surface activity while antimicrobiotic activity is preserved, little is known concerning the effects on synthesis of endogenous surfactant in alveolar type II cells (ATIIC).
  
  
  OBJECTIVE
  To investigate ATIIC viability and surfactant-exocytosis depending on PxB and/or surfactant exposure.
  
  
  METHODS
  ATIIC were isolated from rat lungs as previously described and were cultivated for 48 h. After incubation for a period of 1-5 h with either PxB (0.05 or 0.1 mg/ml), modified porcine surfactant (5 or 10 mg/ml) or mixtures of both, viability and exocytosis (spontanously and after stimulation) were determined by fluorescence staining of intracellular surfactant.
  
  
  RESULTS
  PxB 0.1 mg/ml, but not porcine surfactant or porcine surfactant plus PxB reduces ATIIC-viability. Only PxB alone, but not in combination with porcine surfactant, rapidly reduces fluorescence in ATIIC at maximum within 3 h, indicating stimulation of exocytosis. Subsequent ionomycin-stimulation does not further increase exocytosis of PxB incubated ATIIC. In presence of surfactant, stimulating effects of PxB and ionomycin on exocytosis are reduced.
  
  
  CONCLUSIONS
  PxB alone shows negative effects on ATIIC, which are counterbalanced in mixtures with surfactant. So far, our studies found no results discouraging the concept of a combined treatment with PxB and surfactant mixtures.
authors.affiliation: Department of Pediatrics, University of Luebeck, Luebeck, Germany. guido.stichtenoth@uksh.de
authors.forename: Guido
authors.initials: G
authors.lastname: Stichtenoth
authors.forename: Egbert
authors.initials: E
authors.lastname: Herting
authors.forename: Mario
authors.initials: M
authors.lastname: Rüdiger
authors.forename: Andreas
authors.initials: A
authors.lastname: Wemhöner
mesh_terms: D056809:Alveolar Epithelial Cells / Q000166:cytology* / Q000187:drug effects; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology; D011112:Polymyxin B / Q000494:pharmacology*; D011663:Pulmonary Surfactants / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D034421:Sus scrofa
chemical_list: D011663:Pulmonary Surfactants; D015759:Ionomycin; D011112:Polymyxin B