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

Abstract

Serum-free primary cultures of human bronchial epithelial cells and freshly isolated samples of human bronchial epithelium were used to investigate basal expression of the cytochrome P450 enzyme CYP2E1 and its activation or induction by ethanol in bronchial epithelial cells. The cultures consisted of > or =95% cells of epithelial characteristics as determined 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 analysis, basal expression of mRNAs coding for CYP2B7, CYP2F1 and CYP2E1 were detected in cultures from several donors. The basal expression of CYP2E1 protein and mRNA showed differences between the donors. The mRNA was detected even in cultures from higher generations and increased in some cultures over time. The CYP2E1 protein content was low and in most cultures of generations 2-5 could not be detected by immunoblot analysis of native protein extracts. Nevertheless, in some cases immunoreactive CYP2E1 protein was present in monolayers obtained from the fourth and fifth transfer (18-week 'generation'). CYP2E1 activity was measured via 6-hydroxylation of chlorzoxazone either by a destructive assay using cell lysate or by a non-invasive assay using the medium of cell cultures. In short-term cultured isolated bronchial epithelium, ethanol treatment increased CYP2E1 activity by up to 5-fold within 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. Differentiated primary human cells in culture may be useful tools as model systems for the evaluation of CYP2E1-driven processes in man.