Plasmin(ogen) promotes renal interstitial fibrosis by promoting epithelial-to-mesenchymal transition: role of plasmin-activated signals.
Plasminogen (Plg) activator inhibitor-1 (PAI-1) is an important fibrosis-promoting molecule. Whether this effect can be attributed to PAI-1's activity as an inhibitor of plasmin generation is debated. This study was designed to investigate the role of Plg in renal fibrosis using in vivo and in vitro approaches. Plg-deficient (Plg-/-) and wild-type (Plg+/+) C57BL/6 mice were subjected to unilateral ureteral obstruction or sham surgery (n = 8/group; sham, days 3, 7, 14, and 21). Plg deficiency was confirmed by the absence of Plg mRNA, protein, and plasmin activity. After 21 d of unilateral ureteral obstruction, total kidney collagen was significantly reduced by 35% in the Plg-/- mice. Epithelial-to-mesenchymal transition (EMT), as typified by tubular loss of E-cadherin and acquisition of alpha-smooth muscle actin, was also significantly reduced in Plg-/- mice, 76% and 50%, respectively. Attenuation of EMT and fibrosis severity in the Plg-/- mice was associated with significantly lower levels of phosphorylated extracellular signal-regulated kinase (ERK) and active TGF-beta. In vitro, addition of plasmin (20 microg/ml) to cultures of murine tubular epithelial cells initiated ERK phosphorylation within minutes, followed by phenotypic transition to fibroblast-specific protein-1+, alpha-smooth muscle actin+, fibronectin-producing fibroblast-like cells. Both plasmin-induced ERK activation and EMT were significantly blocked in vitro by the protease-activated receptor-1 (PAR-1) silencing RNA; by pepducin, a specific anti-PAR-1 signaling peptide; and by the ERK kinase inhibitor UO126. Plasmin-induced ERK phosphorylation was enhanced in PAR-1-overexpressing tubular cells. These findings support important profibrotic roles for plasmin that include PAR-1-dependent ERK signaling and EMT induction.
Zhang
Guoqiang
G
Children's Hospital & Regional Medical Center, 4800 Sand Point Way NE, Division of Nephrology, Mail Stop M1-5, Seattle, WA 98105, USA.
Kernan
Kelly A
KA
Collins
Sarah J
SJ
Cai
Xiaohe
X
López-Guisa
Jesús M
JM
Degen
Jay L
JL
Shvil
Yigal
Y
Eddy
Allison A
AA
D000199:Actins / Q000378:metabolism; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D015820:Cadherins / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D003094:Collagen / Q000378:metabolism*; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D005341:Fibrinolysin / Q000494:pharmacology*; D005355:Fibrosis / Q000378:metabolism; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D007674:Kidney Diseases / Q000209:etiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D017395:Plasminogen Activator Inhibitor 1 / Q000172:deficiency / Q000378:metabolism*; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014517:Ureteral Obstruction; D010975:Platelet Aggregation Inhibitors
D000199:Actins; D002070:Butadienes; D015820:Cadherins; D004791:Enzyme Inhibitors; D009570:Nitriles; D017395:Plasminogen Activator Inhibitor 1; D044463:Receptor, PAR-1; D016212:Transforming Growth Factor beta; C113580:U 0126; D003094:Collagen; D048049:Extracellular Signal-Regulated MAP Kinases; D005341:Fibrinolysin; D010975:Platelet Aggregation Inhibitors