Increased expression of plasminogen activator and plasminogen activator inhibitor during liver fibrogenesis of rats: role of stellate cells.
OBJECTIVE
Plasminogen activators and plasminogen activator inhibitors are important regulators of the balance between the proteolytic and antiproteolytic activities that determine extracellular matrix turnover. We examined the expression of plasminogen activator-plasmin system components in experimental liver fibrosis of rats.


METHODS
Liver fibrosis was produced in rats by injecting carbon tetrachloride for 6 to 12 weeks. Gene expression for plasminogen activator inhibitor-1 (PAI-1), urokinase and tissue plasminogen activators (uPA and tPA), urokinase plasminogen activator receptor (uPAR), and transforming growth factor-beta1 (TGF-beta1) was examined by Northern analysis. Western analysis was performed to detect protein expression of PAI-1, uPA and uPAR. An immunohistochemical study was performed to detect the localization of PAI-1. Additionally, primary cultured liver cells were examined by Northern and Western analyses for this protein with or without prior incubation with TGF-beta1.


RESULTS
At 6 weeks, when fibrosis had occurred, uPA and uPAR mRNAs had increased 2.8-fold and 1.8-fold, respectively; PAI-1 and tPA mRNA levels were unchanged. At the cirrhotic stage (9 to 12 weeks), mRNA levels for PAI-1, uPA, uPAR and tPA were all increased. Western analysis also showed increased uPA and uPAR expressions in fibrotic liver, and increased PAI-1, uPA and uPAR expressions in cirrhotic liver. PAI-1 protein was also demonstrated immunohistochemically along sinusoids, vessels, and bile duct cells of normal and fibrotic liver. In liver cell cultures, Kupffer cells, hepatocytes, and especially stellate cells, expressed PAI-1. Expression was enhanced in stellate cells cultured from fibrotic or cirrhotic liver or stimulated in vitro with TGF-beta1.


CONCLUSIONS
Though increased uPA and uPAR may act on matrix degradation in fibrotic liver, increased PAI-1 together with uPA, uPAR and tPA are associated with overall inhibition of matrix degradation in cirrhotic liver. Hepatic stellate cells are an important source of PAI-1 during liver fibrosis.
Zhang
L P
LP
Third Department of Internal Medicine, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
Takahara
T
T
Yata
Y
Y
Furui
K
K
Jin
B
B
Kawada
N
N
Watanabe
A
A
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D007150:Immunohistochemistry; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008106:Liver Cirrhosis, Experimental / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology; D008297:Male; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D010960:Plasminogen Activators / Q000378:metabolism*; D015849:Plasminogen Inactivators / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D016212:Transforming Growth Factor beta / Q000235:genetics; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism
D017395:Plasminogen Activator Inhibitor 1; D015849:Plasminogen Inactivators; C524900:Plaur protein, rat; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D016212:Transforming Growth Factor beta; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator