Pentoxifylline downregulates α (I) collagen expression by the inhibition of Iκbα degradation in liver stellate cells

Overproduction of collagen (I) by activated hepatic stellate cells is a critical step in the development of liver fibrosis. It has been established that these cells express interleukin (IL)-6 and respond to this cytokine with an increase in alpha(I) collagen. Pentoxifylline, a methylxanthine derivate, has been reported to have antifibrotic properties, but the mechanism responsible for this effect is unknown. The aim of this study was to determine the effect of pentoxifylline on acetaldehyde-induced collagen production in a rat hepatic stellate cell line (CFSC-2G cells). Cells were treated with 100 mu M acetaldehyde and 200 mu M pentoxifyline for 3 h. IL-6 and alpha(I) collagen messenger RNA (mRNA) were determined by reverse transcriptase polymerase chain reaction (RT-PCR) assay. NF kappa B activation was determined by electrophoretic mobility shift assay. To corroborate NF kappa B participation in pentoxifylline effect, cells were pretreated with 10 mu M TPCK, a NF kappa B inhibitor. I kappa B alpha was determined by Western blot. IL-6 expression decreased significantly in acetaldehyde-pentoxifylline-treated cells. Acetaldehyde-treated cells pretreated with an anti-IL-6 monoclonal antibody did not show any increase in alpha (I) collagen expression. Acetaldehyde-treated cells increased 1.48 times NF kappa B activation, whereas acetaldehyde-pentoxifylline-treated cells decreased NF kappa B activation to control values. TPCK pretreated acetaldehyde cells did not present NF kappa B activation. To corroborate NF kappa B participation in pentoxifylline effect, I kappa B alpha was determined. I kappa B alpha protein level decreased 50% in acetaldehyde-treated cells, while acetaldehyde-pentoxifylline-treated cells showed I kappa B alpha control cells value. The data suggest that acetaldehyde induced alpha(I) collagen and IL-6 expression via NF kappa B activation. Pentoxifylline prevents acetaldehyde-induced alpha(I) collagen and IL-6 expression by a mechanism dependent on I kappa B alpha degradation, which in turn blocks NF kappa B activation.