Expression of cytochromes P-450 2E1, 3A4 and 1A1/1A2 in growing and confluent human HepG2 hepatoma cells - Effect of ethanol

In cultured human hepatoma HepG2 cells, cytochrome (CYP) 1A-associated 7-et hoxyresorufin-O-deethylase (EROD), CYP 3A-associated benzyloxyresorufin O-d ebenzylase (BROD) and CYP 2E1-associated p-nitrophenol-hydroxylase (PNPH) d ecreased during time in culture. The enzyme activities in cells at confluen ce were 35-60% of the activities in cells 24 hours after seeding. Similarly , CYP 3A and CYP 2E1 proteins were present at higher concentrations in grow ing (G) than in confluent (C) HepG2 cells. CYP 1A1/1A2? protein was not det ected, neither in G nor in C HepG2 cells but was strongly induced by 3-meth ylcholanthrene (3-MC) treatment. Ethanol (EtOH) was shown to increase CYP 2 E1 and CYP 3A proteins and CYP 1A1/1A2-, CYP 2E1- and CYP 3A-associated mix ed-function oxidase activities (MFOs) in HepG2 cells, as has been previousl y reported for primary cultures of human hepatocytes. These effects were ob served only at the beginning of culture, in growing HepG2 cells, demonstrat ing the influence of the growth stage of HepG2 cells on their response to E tOH treatment. This is, to our knowledge, the first report on increases in CYP proteins and associated MFOs by EtOH in HepG2 cells, it suggests that g rowing HepG2 cells provide a useful ill vitro model system in which to stud y the regulation of human CYPs by EtOH. (C) 1999 Elsevier Science Ltd. All rights reserved reserved.