Expression of cytochrome P450 2E1 in normal human bronchial epithelial cells and activation by ethanol in culture

Serum-free primary cultures of human bronchial epithelial cells and freshly isolated samples of human bronchial epithelium were used to investigate ba sal expression of the cytochrome P450 enzyme CYP2E1 and its activation or i nduction by ethanol in bronchial epithelial cells. The cultures consisted o f greater than or equal to 95% cells of epithelial characteristics as deter mined by transmission electron microscopy and immunohistochemical staining. Monolayers were obtained from explants over a period of several months via transfer of tissue into new dishes ('generations' 1-5). Using RT-PCR analy sis, basal expression of mRNAs coding for CYP2B7, CYP2F1 and CYP2E1 were de tected in cultures from several donors. The basal expression of CYP2E1 prot ein and mRNA showed differences between the donors. The mRNA was detected e ven in cultures from higher generations and increased in some cultures over time. The CYP2E1 protein content was low and in most cultures of generatio ns 2-5 could not be detected by immunoblot analysis of native protein extra cts. Nevertheless, in some cases immunoreactive CYP2E1 protein was present in monolayers obtained from the fourth and fifth transfer (18-week 'generat ion'). CYP2E1 activity was measured via 6-hydroxylation of chlorzoxazone ei ther by a destructive assay using cell lysate or by a non-invasive assay us ing the medium of cell cultures. In short-term cultured isolated bronchial epithelium, ethanol treatment increased CYP2E1 activity by up to 5-fold wit hin 4 days but with inter-individual differences. In cells up to 4 weeks in culture, CYP2E1 activity remained inducible by a single dose of ethanol. D ifferentiated primary human cells in culture may be useful tools as model s ystems for the evaluation of CYP2E1-driven processes in man.