Expression and DNA-binding activity of C/EBPα and C/EBPβ in human liver and differentiated primary hepatocytes

Background/Aims: Limited information is available on the expression and role of C/EBP factors in human liver and hepatocytes. We investigated the expression and DNA-binding activity of C/EBPα and C/EBPβ in human liver needle biopsies, surgical lobectomies and differentiated cultured hepatocytes derived from lobectomies. Methods: RNA and protein extracts were analyzed by RNAse protection, immunoblot and gel shift assays. Results: C/EBP mRNAs, isoforms and DNA-binding activities were low/undetectable in lobectomies. In contrast, several C/EBPα (47, 45, 35 and 33 kDa) and C/EBPβ isoforms (47, 43, 40, 35 and 21 kDa) were observed in needle biopsies. In cultured hepatocytes, the C/EBP expression pattern dramatically changed with time. C/EBPα mRNA and the 45 kDa isoform increased in parallel, reaching a maximum after 3–4 weeks coincident with weak DNA-binding activity. C/EBPβ mRNA and isoform expression increased rapidly reaching a plateau within 1–2 weeks; all C/EBPβ isoforms were phosphorylated. C/EBPβ exhibited greater DNA-binding activity than C/EBPα, and this activity paralleled C/EBPβ isoform expression. Conclusions: C/EBP isoforms exhibit markedly different expression patterns in lobectomies, needle biopsies and cultured hepatocytes. Stress stimuli during and/or after surgery for lobectomy resections may account for this difference. The pattern of C/EBP isoform expression in long-term highly differentiated cultured hepatocytes is close to that observed in needle biopsies.