Elk-3 Contributes to the Progression of Liver Fibrosis by Regulating the Epithelial-Mesenchymal Transition.

BACKGROUND/AIMS: The role of Elk-3 in the epithelial-mesenchymal transition (EMT) during liver fibrogenesis remains unclear. Here, we determined the expression of Elk-3 in in vitro and in vivo models and in human liver fibrotic tissues. We also investigated the molecular relationships among Elk-3, early growth response-1 (Egr-1), and the mitogen activated protein kinases (MAPK) pathway during EMT in hepatocytes.

METHODS

We established an in vitro EMT model in which normal mouse hepatocyte cell lines were treated with transforming growth factor (TGF)-β1 and a CCl₄-induced liver fibrosis model. Characteristics of EMT were determined by evaluating the expression levels of related markers. The expression of Elk-3 and its target Egr-1 were analyzed using Western blotting. Gene silencing of Elk-3 was performed using an siRNA knockdown system.

RESULTS

The expression levels of mesenchymal markers were increased during TGF-β1-induced EMT of hepatocytes. The expression levels of Elk-3 and Egr-1 were significantly (p<0.05) increased during the EMT of hepatocytes, in CCl₄-induced mouse liver fibrotic tissues, and in human liver cirrhotic tissues. Silencing of Elk-3 and inhibition of the Ras-Elk-3 pathway with an inhibitor suppressed the expression of EMT-related markers. Moreover, Elk-3 expression was regulated by p38 MAPK phosphorylation during EMT.

CONCLUSIONS

Elk-3 contributes to the progression of liver fibrosis by modulating the EMT via the regulation of Egr-1 under MAPK signaling.