title: Salbutamol up-regulates matrix metalloproteinase-9 in the alveolar space in the acute respiratory distress syndrome.
abstract: OBJECTIVE
  Acute respiratory distress syndrome (ARDS) is characterized by alveolar-capillary barrier damage. Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of ARDS. In the Beta Agonists in Acute Lung Injury Trial, intravenous salbutamol reduced extravascular lung water (EVLW) in patients with ARDS at day 4 but not inflammatory cytokines or neutrophil recruitment. We hypothesized that salbutamol reduces MMP activity in ARDS.
  
  
  METHODS
  MMP-1/-2/-3/-7/-8/-9/-12/-13 was measured in supernatants of distal lung epithelial cells, type II alveolar cells, and bronchoalveolar lavage (BAL) fluid from patients in the Beta Agonists in Acute Lung Injury study by multiplex bead array and tissue inhibitors of metalloproteinases (TIMPs)-1/-2 by enzyme-linked immunosorbent assay. MMP-9 protein and activity levels were further measured by gelatin zymography and fluorokine assay.
  
  
  RESULTS
  BAL fluid MMP-1/-2/-3 declined by day 4, whereas total MMP-9 tended to increase. Unexpectedly, salbutamol augmented MMP-9 activity. Salbutamol induced 33.7- and 13.2-fold upregulation in total and lipocalin-associated MMP-9, respectively at day 4, compared with 2.0- and 1.3-fold increase in the placebo group, p < 0.03. Salbutamol did not affect BAL fluid TIMP-1/-2. Net active MMP-9 was higher in the salbutamol group (4222 pg/mL, interquartile range: 513-7551) at day 4 compared with placebo (151 pg/mL, 124-2108), p = 0.012. Subjects with an increase in BAL fluid MMP-9 during the 4-day period had lower EVLW measurements than those in whom MMP-9 fell (10 vs. 17 mL/kg, p = 0.004): change in lung water correlated inversely with change in MMP-9, r = -.54, p = 0.0296. Salbutamol up-regulated MMP-9 and down-regulated TIMP-1/-2 secretion in vitro by distal lung epithelial cells. Inhibition of MMP-9 activity in cultures of type II alveolar epithelial cells reduced wound healing.
  
  
  CONCLUSIONS
  Salbutamol specifically up-regulates MMP-9 in vitro and in vivo in patients with ARDS. Up-regulated MMP-9 is associated with a reduction in EVLW. MMP-9 activity is required for alveolar epithelial wound healing in vitro. Data suggest MMP-9 may have a previously unrecognized beneficial role in reducing pulmonary edema in ARDS by improving alveolar epithelial healing.
authors.affiliation: Respiratory Medicine Research Programme, Centre for Infection and Immunity, Queen's University, Belfast, United Kingdom.
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: O'Kane
authors.forename: Scott W
authors.initials: SW
authors.lastname: McKeown
authors.forename: Gavin D
authors.initials: GD
authors.lastname: Perkins
authors.forename: Chris R
authors.initials: CR
authors.lastname: Bassford
authors.forename: Fang
authors.initials: F
authors.lastname: Gao
authors.forename: David R
authors.initials: DR
authors.lastname: Thickett
authors.forename: Danny F
authors.initials: DF
authors.lastname: McAuley
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000420:Albuterol / Q000494:pharmacology*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D018929:Cell Culture Techniques; D004847:Epithelial Cells / Q000187:drug effects; D015633:Extravascular Lung Water / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D045726:Metalloproteases / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D012128:Respiratory Distress Syndrome / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D019715:Tissue Inhibitor of Metalloproteinase-1; D019716:Tissue Inhibitor of Metalloproteinase-2; D045726:Metalloproteases; D000420:Albuterol