title: Low-dose endotoxin inhalation in healthy volunteers--a challenge model for early clinical drug development.
abstract: BACKGROUND
  Inhalation of endotoxin (LPS) induces a predominantly neutrophilic airway inflammation and has been used as model to test the anti-inflammatory activity of novel drugs. In the past, a dose exceeding 15-50 μg was generally needed to induce a sufficient inflammatory response. For human studies, regulatory authorities in some countries now request the use of GMP-grade LPS, which is of limited availability. It was therefore the aim of this study to test the effect and reproducibility of a low-dose LPS challenge (20,000 E.U.; 2 μg) using a flow- and volume-controlled inhalation technique to increase LPS deposition.
  
  
  METHODS
  Two to four weeks after a baseline sputum induction, 12 non-smoking healthy volunteers inhaled LPS on three occasions, separated by at least 4 weeks. To modulate the inflammatory effect of LPS, a 5-day PDE4 inhibitor (Roflumilast) treatment preceded the last challenge. Six hours after each LPS inhalation, sputum induction was performed.
  
  
  RESULTS
  The low-dose LPS inhalation was well tolerated and increased the mean percentage of sputum neutrophils from 25% to 72%. After the second LPS challenge, 62% neutrophils and an increased percentage of monocytes were observed. The LPS induced influx of neutrophils and the cumulative inflammatory response compared with baseline were reproducible. Treatment with Roflumilast for 5 days did not have a significant effect on sputum composition.
  
  
  CONCLUSIONS
  The controlled inhalation of 2 μg GMP-grade LPS is sufficient to induce a significant neutrophilic airway inflammation in healthy volunteers. Repeated low-dose LPS challenges potentially result in a small shift of the neutrophil/monocyte ratio; however, the cumulative response is reproducible, enabling the use of this model for "proof-of-concept" studies for anti-inflammatory compounds during early drug development.
authors.affiliation: Department of Clinical Airway Research, Fraunhofer Institute for Toxicology and Experimental Medicine, 30625 Hannover, Germany.
authors.forename: Ole
authors.initials: O
authors.lastname: Janssen
authors.forename: Frank
authors.initials: F
authors.lastname: Schaumann
authors.forename: Olaf
authors.initials: O
authors.lastname: Holz
authors.forename: Bianca
authors.initials: B
authors.lastname: Lavae-Mokhtari
authors.forename: Lutz
authors.initials: L
authors.lastname: Welker
authors.forename: Carla
authors.initials: C
authors.lastname: Winkler
authors.forename: Heike
authors.initials: H
authors.lastname: Biller
authors.forename: Norbert
authors.initials: N
authors.lastname: Krug
authors.forename: Jens M
authors.initials: JM
authors.lastname: Hohlfeld
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000631:Aminopyridines / Q000008:administration & dosage*; D001549:Benzamides / Q000008:administration & dosage*; D003521:Cyclopropanes / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D004731:Endotoxins / Q000008:administration & dosage* / Q000009:adverse effects* / Q000276:immunology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D058988:Phosphodiesterase 4 Inhibitors / Q000008:administration & dosage; D011014:Pneumonia / Q000139:chemically induced* / Q000188:drug therapy* / Q000276:immunology; D015203:Reproducibility of Results; D012107:Research Design; D013183:Sputum / Q000276:immunology; D055815:Young Adult
chemical_list: D000631:Aminopyridines; D001549:Benzamides; D003521:Cyclopropanes; D004731:Endotoxins; D008070:Lipopolysaccharides; D058988:Phosphodiesterase 4 Inhibitors; C424423:Roflumilast
references.citation: Am J Respir Crit Care Med. 2005 Oct 1;172(7):878-84
references.pmid: 15994467
references.citation: Respir Res. 2011 Oct 26;12:140
references.pmid: 22029856
references.citation: Clin Pharmacokinet. 2010 Sep;49(9):589-606
references.pmid: 20690782
references.citation: Am J Respir Crit Care Med. 2001 Jun;163(7):1591-8
references.pmid: 11401879
references.citation: Respir Med. 2006 Mar;100(3):519-28
references.pmid: 16039108
references.citation: Br J Clin Pharmacol. 2012 Dec;74(6):1023-32
references.pmid: 22469312
references.citation: Contrib Microbiol. 2007;14:83-100
references.pmid: 17684334
references.citation: Crit Care Med. 2002 Jan;30(1 Supp):S64-S73
references.pmid: 11891406
references.citation: J Endotoxin Res. 2006;12(6):367-74
references.pmid: 17254391
references.citation: J Clin Pharmacol. 2005 May;45(5):498-503
references.pmid: 15831772
references.citation: J Endotoxin Res. 2002;8(4):241-52
references.pmid: 12230914
references.citation: Respir Med. 2004 Nov;98(11):1087-92
references.pmid: 15526809
references.citation: Am J Respir Crit Care Med. 1997 Oct;156(4 Pt 1):1157-64
references.pmid: 9351616
references.citation: Inhal Toxicol. 2011 Jun;23(7):392-406
references.pmid: 21639708
references.citation: Pulm Pharmacol Ther. 2008 Aug;21(4):616-23
references.pmid: 18374614
references.citation: Am Rev Respir Dis. 1992 Aug;146(2):352-7
references.pmid: 1489124
references.citation: J Endotoxin Res. 2004;10(2):71-84
references.pmid: 15119998
references.citation: J Allergy Clin Immunol. 2005 Feb;115(2):345-50
references.pmid: 15696093
references.citation: Inflammation. 2012 Feb;35(1):33-8
references.pmid: 21207124
references.citation: Ann Allergy Asthma Immunol. 2008 Mar;100(3):206-15
references.pmid: 18426139
references.citation: Inhal Toxicol. 2010 Jul;22(8):648-56
references.pmid: 20540623
references.citation: PLoS One. 2012;7(8):e43709
references.pmid: 22952743
references.citation: J Environ Monit. 2003 Dec;5(6):953-8
references.pmid: 14710938
references.citation: Eur Respir J. 2005 Aug;26(2):363-4
references.pmid: 16055890
references.citation: J Pharm Sci. 2000 Jun;89(6):724-31
references.pmid: 10824130
references.citation: Pulm Pharmacol Ther. 2007;20(6):676-83
references.pmid: 17045826
references.citation: Inflamm Res. 2001 May;50(5):254-61
references.pmid: 11409488
references.citation: J Clin Pharmacol. 2007 Aug;47(8):1005-13
references.pmid: 17660483
references.citation: Chest. 1999 Mar;115(3):829-35
references.pmid: 10084499
references.citation: Eur Respir J Suppl. 2002 Sep;37:1s-2s
references.pmid: 12361359
references.citation: Thorax. 2007 Dec;62(12):1081-7
references.pmid: 17573446