Transcriptional Activation of the Heme Oxygenase Gene by Heme and Cadmium in Mouse Hepatoma Cells

Laminin γ1 chain is present in all basement membranes and is expressed at high levels in various diseases, such as hepatic fibrosis. We have identified cis- and trans-acting elements involved in the regulation of this gene in normal rat liver, as well as in hepatocyte primary cultures and hepatoma cell lines. Northern-blot analyses showed that laminin γ1 mRNA was barely detectable in freshly isolated hepatocytes and expressed at high levels in hepatocyte primary cultures, as early as 4 h after liver dissociation. Actinomycin D and cycloheximide treatment in vivo and in vitro indicated that laminin γ1 overexpression in cultured hepatocytes was under the control of transcriptional mechanisms. Transfection of deletion mutants of the 5´ flanking region of murine LAMC1 gene in hepatoma cells that constitutively express laminin γ1 indicated that regulatory elements were located between -594 bp and -94 bp. This segment included GC- and CTC-containing motifs. Gel-shift analyses showed that two complexes were resolved with different affinity for the CTC sequence depending on the location of the GC box. The pattern of complex formation with nuclear factors from freshly isolated and cultured hepatocytes was different from that obtained with total liver and similar to that with hepatoma cells. Southwestern analysis indicated that several polypeptides bound the CTC-rich sequence. Affinity chromatography demonstrated that a Mr 60000 polypeptide was a major protein binding to the CTC motif. This polypeptide is probably involved in the transcriptional activation of various proto-oncogenes and extracellular matrix genes that are expressed at high levels in both hepatoma cells and early hepatocyte cultures.

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Phenobarbital inhibits calpain activity and expression in mouse hepatoma cells

Biological Chemistry ◽

10.1515/hsz-2015-0223 ◽

2016 ◽

Vol 397 (1) ◽

pp. 91-96 ◽

Cited By ~ 5

Author(s):

Nicola Groll ◽

Ferdinand Kollotzek ◽

Jens Goepfert ◽

Thomas O. Joos ◽

Michael Schwarz ◽

...

Keyword(s):

Cell Proliferation ◽

Transcriptional Regulation ◽

Antiepileptic Drug ◽

Signaling Pathway ◽

Constitutive Androstane Receptor ◽

Hepatoma Cells ◽

Liver Cells ◽

Mrna Levels ◽

Calpain Activity ◽

Mouse Hepatoma

Abstract The antiepileptic drug phenobarbital (PB) exerts hepatic effects related to cell proliferation and tumorigenesis which are closely linked to the Wnt/β-catenin signaling pathway. This pathway is, amongst others, regulated by calpain proteases. We now identified PB as an inhibitor of Wnt/β-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.

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