Published ahead of print on June 22, 2006, doi:10.1165/rcmb.2006-0040OC Am. J. Respir. Cell Mol. Biol., Volume 35, Number 6, December 2006, 628-638 A more recent version of this article appeared on December 1, 2006
Submitted on January 27, 2006 Induction of the Plasminogen Activator System by Mechanical Stimulation of Human Bronchial Epithelial CellsEric K Chu1*,1 Department of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston, MA, USA; Physiology Program, Harvard School of Public Health, Boston, MA, USA, 2 Physiology Program, Harvard School of Public Health, Boston, MA, USA, 3 Department of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston, MA, USA, 4 Children's Hospital Informatics Program, Children's Hospital Boston, Boston, MA, USA * To whom correspondence should be addressed. E-mail: e.chu{at}utoronto.ca, echu@partners.org.
Mechanical stimulation of the airway epithelium, as would occur during bronchoconstriction is a potent stimulus and can activate profibrotic pathways. We used DNA microarray technology to examine gene expression in compressed normal human bronchial epithelial cells (NHBE). Compressive stress applied continuously over an 8 hour period to NHBE cells led to the upregulation of several families of genes including a family of plasminogen related genes that were previously not known to be regulated in this system. Real-time PCR demonstrated a peak increase in gene expression of 8.0 fold for urokinase plasminogen activator (uPA), 16.2 fold for urokinase plasminogen activator receptor (uPAR), 4.2 fold for plasminogen activator inhibitor-1 (PAI-1) and 3.9 fold for tissue plasminogen activator (tPA). Compressive stress also increased uPA protein levels in the cell lysates (112.0 vs 82.0 ng/ml, p=0.0004), and increased uPA (4.7 vs 3.3 ng/mL p=0.02), uPAR (1.3 vs 0.86 ng/mL p=0.007) and PAI-1 (50 vs 36 ng/mL p=0.006) protein levels in cell culture media. Functional studies demonstrated increased urokinase dependent plasmin generation in compression stimulated cells (0.0090 vs 0.0033 OD/min, p=0.03). In addition, compression led to increased activation of matrix metalloproteinase (MMP)-9 and MMP2 in a urokinase dependent manner. In post-mortem human lung tissue, we observed an increase in epithelial uPA and uPAR immunostaining in the airways of two patients who died in status asthmaticus compared to minimal immunoreactivity noted in airways from seven non-asthmatic lung donors. Together these observations suggest an integrated response of airway epithelial cells to mechanical stimulation, acting through the plasminogen activating system to modify the airway micro-environment.
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