Induction of tissue factor by urokinase in lung epithelial cells and in the lungs.
BACKGROUND
Urokinase-type plasminogen activator (uPA) regulates extracellular proteolysis in lung injury and repair. Although alveolar expression of uPA increases, procoagulant activity predominates.


OBJECTIVE
This study was designed to investigate whether uPA alters the expression of tissue factor (TF), the major initiator of the coagulation cascade, in lung epithelial cells (ECs).


METHODS
Bronchial, primary airway ECs and C57B6 wild-type, uPA-deficient (uPA(-/-)) mice were exposed to phosphate-buffered saline, uPA, or LPS. Immunohistochemistry, protein, cellular, and molecular techniques were used to assess TF expression and activity.


RESULTS
uPA enhanced TF mRNA and protein expression, and TF-dependent coagulation in lung ECs. uPA-induced expression of TF involves both increased synthesis and enhanced stabilization of TF mRNA. uPA catalytic activity had little effect on induction of TF. By contrast, deletion of the uPA receptor binding growth factor domain from uPA markedly attenuated the induction of TF, suggesting that uPA receptor binding is sufficient for TF induction. Lung tissues of uPA-deficient mice expressed less TF protein and mRNA compared with wild-type mice. In addition, intratracheal instillation of mouse uPA increased TF mRNA and protein expression and accelerated coagulation in lung tissues. uPA(-/-) mice exposed to LPS failed to induce TF.


CONCLUSIONS
uPA increased TF expression and TF-dependent coagulation in the lungs of mice. We hypothesize that uPA-mediated induction of TF occurs in lung ECs to promote increased fibrin deposition in the airways during acute lung injury.
Shetty
Sreerama
S
Department of Specialty Care Services, The Texas Lung Injury Institute, University of Texas Health Center at Tyler, 11937 US Highway 271, Tyler, TX 75708, USA. sreerama.shetty@uthct.edu
Bhandary
Yashodhar P
YP
Shetty
Shwetha K
SK
Velusamy
Thirunavukkarasu
T
Shetty
Praveenkumar
P
Bdeir
Khalil
K
Gyetko
Margaret R
MR
Cines
Douglas B
DB
Idell
Steven
S
Neuenschwander
Pierre F
PF
Ruppert
Clemens
C
Guenther
Andreas
A
Abraham
Edward
E
Shetty
Rashmi S
RS
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D018929:Cell Culture Techniques; D004847:Epithelial Cells / Q000378:metabolism*; D005337:Fibrin / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D013925:Thromboplastin / Q000378:metabolism*; D015533:Transcriptional Activation; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D005337:Fibrin; D013925:Thromboplastin; D014568:Urokinase-Type Plasminogen Activator