title: Plasma neutrophil elastase and elafin imbalance is associated with acute respiratory distress syndrome (ARDS) development.
abstract: BACKGROUND
  We conducted an exploratory study of genome-wide gene expression in whole blood and found that the expression of neutrophil elastase inhibitor (PI3, elafin) was down-regulated during the early phase of ARDS. Further analyses of plasma PI3 levels revealed a rapid decrease during early ARDS development. PI3 and secretory leukocyte proteinase inhibitor (SLPI) are important low-molecular-weight proteinase inhibitors produced locally at neutrophil infiltration site in the lung. In this study, we tested the hypothesis that an imbalance between neutrophil elastase (HNE) and its inhibitors in blood is related to the development of ARDS.
  
  
  RESULTS
  PI3, SLPI, and HNE were measured in plasma samples collected from 148 ARDS patients and 63 critical ill patients at risk for ARDS (controls). Compared with the controls, the ARDS patients had higher HNE, but lower PI3, at the onset of ARDS, resulting in increased HNE/PI3 ratio (mean = 14.5; 95% CI, 10.9-19.4, P<0.0001), whereas plasma SLPI was not associated with the risk of ARDS development. Although the controls had elevated plasma PI3 and HNE, their HNE/PI3 ratio (mean = 6.5; 95% CI, 4.9-8.8) was not significantly different from the healthy individuals (mean = 3.9; 95% CI, 2.7-5.9). Before the onset (7-days period prior to ARDS diagnosis), we only observed significantly elevated HNE, but the HNE-PI3 balance remained normal. With the progress from prior to the onset of ARDS, the plasma level of PI3 declined, whereas HNE was maintained at a higher level, tilting the balance toward more HNE in the circulation as characterized by an increased HNE/PI3 ratio. In contrast, three days after ICU admission, there was a significant drop of HNE/PI3 ratio in the at-risk controls.
  
  
  CONCLUSIONS
  Plasma profiles of PI3, HNE, and HNE/PI3 may be useful clinical biomarkers in monitoring the development of ARDS.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. mikewang@hsph.harvard.edu
authors.forename: Zhaoxi
authors.initials: Z
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Rihong
authors.initials: R
authors.lastname: Zhai
authors.forename: Lingsong
authors.initials: L
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Su
authors.forename: Xihong
authors.initials: X
authors.lastname: Lin
authors.forename: Taylor
authors.initials: T
authors.lastname: Thompson
authors.forename: David C
authors.initials: DC
authors.lastname: Christiani
mesh_terms: D000704:Analysis of Variance; D016022:Case-Control Studies; D018450:Disease Progression; D053492:Elafin / Q000097:blood*; D005260:Female; D006801:Humans; D019272:Leukocyte Elastase / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012128:Respiratory Distress Syndrome / Q000097:blood* / Q000201:enzymology* / Q000473:pathology; D053481:Secretory Leukocyte Peptidase Inhibitor / Q000097:blood
chemical_list: D053492:Elafin; C506814:SLPI protein, human; D053481:Secretory Leukocyte Peptidase Inhibitor; D019272:Leukocyte Elastase