Poster Presenter

Paraxanthine, The Primary Metabolite Of Caffeine, Inhibits Connective Tissue Growth Factor, and Collagen α1 Type 1 but not α Smooth Muscle Actin Expression In Transdifferentiating Rat Hepatic Stellate Cells
Olav A Gressner, Birgit Lahme, Axel M. Gressner
Germany

Background: Based on reports of a hepatoprotective effect of coffee consumption, we were the first to give evidence that caffeine and even more potently, its primary metabolite paraxanthine, suppress TGF-β dependent and -independent expression of profibrogenic connective tissue growth factor (CTGF/CCN2) in hepatocytes, thus suggesting this xanthine-alkaloids as potentially therapeutic agents.

Methods: Primary rat HSC transdifferentiating in vitro were treated with different concentrations of paraxanthine for 24h and probed for CTGF, a-smooth muscle actin (aSMA), and collagen α1 type 1 (Col1) expression using Western Blot analysis. Furthermore, a CTGF luciferase gene reporter assay was performed.

Results: CTGF was increasingly expressed during transdifferentiation, which was dose-dependently inhibited by paraxanthine, the latter being particularly effective in the progressive stage of transdifferentiation. A representative hCTGF-luciferase reporter assay performed in 5 day old HSC confirmed the results also on the transcriptional level. This reduction of CTGF expression was furthermore accompanied by a continuous, paraxanthine dependent, reduction of expression of Col1 but not of aSMA throughout the entire process of transdifferentiation.

Conclusions: Our results suggest a suitability of paraxanthine in antagonizing transdifferentiation dependent sensitization of HSC towards TGF-β (Smad2 and Smad3) dependent effects, i.e. CTGF and Col1 expression. Further investigations in this direction are on the way.