title: Proteolytic cleavage of elafin by 20S proteasome may contribute to inflammation in acute lung injury.
abstract: BACKGROUND
  We hypothesise that elafin levels in acute lung injury (ALI) decrease over time due, in part, to proteolytic degradation as observed in other lung diseases.
  
  
  OBJECTIVE
  The aim of this study was to characterise temporal changes in elafin concentration in patients with ALI and to evaluate whether a decrease in elafin levels is due to elevated protease activity.
  
  
  METHODS
  Bronchoalveolar lavage fluid (BALF) was obtained from patients with ALI within 48 h of onset of ALI (day 0), at day 3 and at day 7. Elafin levels were quantified by ELISA. Elafin susceptibility to proteolytic cleavage by ALI BALF was assessed by Western blot and by high-performance liquid chromatography-mass spectrometry.
  
  
  RESULTS
  Elafin levels were found to be significantly increased at the onset of ALI compared with healthy volunteers and fell significantly by day 7 compared with day 0. In contrast, levels of secretory leukocyte protease inhibitor did not decrease over time. This decrease in elafin was due to cleavage by the 20S proteasome which was significantly increased in ALI BALF. Incubation of ALI BALF with the proteasome inhibitor epoxomicin confirmed that 20S proteasome protease activity was responsible for proteolytic cleavage of elafin, resulting in diminished anti-elastase activity. In addition, free neutrophil elastase activity significantly increased in ALI BALF from day 0 to day 7.
  
  
  CONCLUSIONS
  Elafin concentrations fall within the pulmonary compartment over the course of ALI as a result of proteolytic degradation. This loss of elafin may predispose people, in part, to excessive inflammation in ALI.
authors.affiliation: Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK.
authors.forename: Aoife
authors.initials: A
authors.lastname: Kerrin
authors.forename: Sinéad
authors.initials: S
authors.lastname: Weldon
authors.forename: Allen Hung-Kang
authors.initials: AH
authors.lastname: Chung
authors.forename: Thelma
authors.initials: T
authors.lastname: Craig
authors.forename: A John
authors.initials: AJ
authors.lastname: Simpson
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: O'Kane
authors.forename: Danny Francis
authors.initials: DF
authors.lastname: McAuley
authors.forename: Clifford C
authors.initials: CC
authors.lastname: Taggart
mesh_terms: D055371:Acute Lung Injury / Q000378:metabolism / Q000503:physiopathology*; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid; D053492:Elafin / Q000032:analysis / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000494:pharmacology*; D059748:Proteolysis / Q000187:drug effects*; D011994:Recombinant Proteins / Q000378:metabolism; D053481:Secretory Leukocyte Peptidase Inhibitor / Q000032:analysis
chemical_list: D053492:Elafin; D011994:Recombinant Proteins; D053481:Secretory Leukocyte Peptidase Inhibitor; D046988:Proteasome Endopeptidase Complex