Long-term treatment of bile duct-ligated rats with rapamycin (sirolimus) significantly attenuates liver fibrosis: analysis of the underlying mechanisms.
Rapamycin is an immunosuppressant with antiproliferative properties. We investigated whether rapamycin treatment of bile duct-ligated (BDL) rats is capable of inhibiting liver fibrosis and thereby affecting hemodynamics. Following BDL, rats were treated for 28 days with rapamycin (BDL SIR). BDL animals without drug treatment (BDL CTR) and sham-operated animals served as controls. After 28 days, hemodynamics were measured, and livers were harvested for histology/immunohistochemistry. Liver mRNA levels of transforming growth factor (TGF)-beta1, connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF)-beta, cyclin-dependent kinase inhibitor p27(kip) (p27), and cyclin-dependent kinase inhibitor p21(WAF1/CIP1) (p21) were quantified by real-time polymerase chain reaction. Liver protein levels of p27, p21, p70 S6 kinase (p70(s6k)), phosphorylated p70(s6k) (p-p70(s6k)), eukaryotic initiation factor 4E-binding protein (4E-BP1), p-4E-BP1 (Thr37/46), and p-4E-BP1 (Ser65/Thr70) were determined by Western blotting. Portal vein pressure was lower in BDL SIR than in BDL CTR animals. Volume fractions of connective tissue, bile duct epithelial, and desmin- and actin-positive cells were lower in BDL SIR than in BDL CTR rats. On the mRNA level, TGF-beta1, CTGF, and PDGF were decreased by rapamycin. p27 and p21 mRNA did not differ. On the protein level, rapamycin increased p27 and decreased p21 levels. Levels of nonphosphorylated p70(s6k) and 4E-BP1 did not vary between groups, but levels of p-p70(s6k) were decreased by rapamycin. Rapamycin had no effect on p-4E-BP1 (Thr37/46) and p-4E-BP1 (Ser65/Thr70) levels. In BDL rats, rapamycin inhibits liver fibrosis and ameliorates portal hypertension. This is paralleled by decreased levels of TGF-beta1, CTGF, and PDGF. Rapamycin influences the cell cycle by up-regulation of p27, down-regulation of p21, and inhibition of p70(s6k) phosphorylation.
Biecker
Erwin
E
Department of Clinical Pharmacology, University of Berne, Switzerland.
De Gottardi
Andrea
A
Neef
Markus
M
Unternährer
Matthias
M
Schneider
Vreni
V
Ledermann
Monika
M
Sägesser
Hans
H
Shaw
Sidney
S
Reichen
Jürg
J
D000818:Animals; D001652:Bile Ducts / Q000473:pathology; D018797:Cell Cycle Proteins / Q000032:analysis; D049109:Cell Proliferation / Q000187:drug effects; D055513:Connective Tissue Growth Factor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017874:Immediate-Early Proteins / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics; D008026:Ligation; D008106:Liver Cirrhosis, Experimental / Q000378:metabolism / Q000517:prevention & control*; D008297:Male; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D020123:Sirolimus / Q000627:therapeutic use*; D016212:Transforming Growth Factor beta / Q000235:genetics; D053773:Transforming Growth Factor beta1; D025521:Tumor Suppressor Proteins / Q000032:analysis
C526316:CCN2 protein, rat; C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D025521:Tumor Suppressor Proteins; D055513:Connective Tissue Growth Factor; D050760:Cyclin-Dependent Kinase Inhibitor p27; D020123:Sirolimus