Characterisation of the connexin32 promoter and changes in response element complexes in rat liver and hepatocytes during culture associated with oxidative stress.

Hepatic gap junctional intercellular communication (GJIC), mediated principally by connexin 32, provides a mechanism for regulating multicellular activities between neighbouring cells. The control of Cx32 gene expression at the transcriptional level has been investigated in rat liver tissue and in primary rat hepatocytes during culture. Several response elements have been identified and characterised using the electrophoretic mobility shift assay. Nuclear protein extract prepared from rat primary hepatocytes cultured for 2 h gave a larger number of DNA-protein complexes than observed with extracts from liver in vivo, including complexes containing Sp1. In contrast, nuclear extracts prepared from primary rat hepatocytes cultured for 96 h, and subject to oxidative stress, gave altered DNA-protein complexes when compared to those from hepatocytes cultured for 2 h. These results indicate that culture conditions, known to cause a loss of connexin expression, can modulate the transcription of Cx32 in hepatocytes by affecting the regulatory trans/cis-interactions of redox-sensitive zinc finger proteins within the promoter.