Pharmacological application of caffeine inhibits TGF-beta-stimulated connective tissue growth factor expression in hepatocytes via PPARgamma and SMAD2/3-dependent pathways.
OBJECTIVE
Epidemiological studies suggest that coffee drinking is inversely correlated with the risk of development of liver fibrosis but the molecular basis is unknown.


METHODS
We investigated the pharmacological mechanisms involved in caffeine-dependent regulation of CTGF expression, an important modulator protein of fibrogenic TGF-beta, in rat hepatocytes using Western-blot, co-immunoprecipitations, reporter-gene-assays and ELISAs.


RESULTS
It is demonstrated that caffeine, similar to 8-Br-cAMP, suppresses CTGF expression, decreases SMAD2 protein levels and inhibits SMAD1/3-phosphorylation. The SMAD2 level can be restored by a proteasome inhibitor. Additionally, caffeine leads to an up-regulation of PPARgamma expression, that enhances the inhibitory effect of the natural PPARgamma agonist 15-PGJ(2) on CTGF expression by inducing a dissociation of the SMAD2/3-CBP/p300-transcriptional complex.


CONCLUSIONS
We show that caffeine strongly down-modulates TGF-beta-induced CTGF expression in hepatocytes by stimulation of degradation of the TGF-beta effector SMAD 2, inhibition of SMAD3 phosphorylation and up-regulation of the PPARgamma-receptor. Long-term caffeinization might be an option for anti-fibrotic trials in chronic liver diseases.
Gressner
Olav A
OA
Institute of Clinical Chemistry and Pathobiochemistry, RWTH-University Hospital, 52074 Aachen, Germany. ogressner@ukaachen.de
Lahme
Birgit
B
Rehbein
Katharina
K
Siluschek
Monika
M
Weiskirchen
Ralf
R
Gressner
Axel M
AM
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D002110:Caffeine / Q000494:pharmacology*; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism*; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D051899:Smad2 Protein / Q000378:metabolism*; D051900:Smad3 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000494:pharmacology
C477819:15-deoxyprostaglandin J2; C526316:CCN2 protein, rat; D017931:DNA Primers; D047495:PPAR gamma; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor; D015124:8-Bromo Cyclic Adenosine Monophosphate; D002110:Caffeine; D015230:Prostaglandin D2