Phenobarbital inhibits calpain activity and expression in mouse hepatoma cells.

The antiepileptic drug phenobarbital (PB) exerts hepatic effects related to cell proliferation and tumorigenesis which are closely linked to the Wnt/beta-catenin signaling pathway. This pathway is, amongst others, regulated by calpain proteases. We now identified PB as an inhibitor of Wnt/beta-catenin signaling in mouse hepatoma cells. Further analyses revealed that PB inhibits calpain activity, an effect which is at least in parts mediated by a transcriptional regulation of calpain mRNA levels and which is furthermore independent of the constitutive androstane receptor, the known mediator of most effects of PB in liver cells.