Effects of Hypoxia-inducible Factor-1α Chemical Stabilizer, CoCl2 and Hypoxia on Gene Expression of CYP3As in Human Fetal Liver Cells

Distinctive response patterns of CYP3A4 and CYP3A7 to cobalt chloride (CoCl2) in human fetal liver (HFL) cells were observed and compared with those under hypoxic conditions. The expression levels of CYP3A4 and CYP3A7 mRNAs were decreased by CoCl2 and hypoxia, although significance could not be determined in HFL cells cultured under 3% O-2. The hypoxia-inducible factor-1 alpha (HIF-1 alpha) protein content in HFL cells was significantly increased by CoCl2 and 3% O-2. Transcriptional activities of CYP3A4 and CYP3A7 were not altered by 3% 02 when reporter plasmids containing the promoter region ranging up to about 10 kb and 12 kb upstream, respectively, were transfected into HFL cells, although the activity was significantly suppressed by CoCl2. These results suggested that the mechanisms controlling CYP3A gene expression of HIF-1 alpha chemical stabilizer in fetal hepatocytes might be different from those in adult hepatocytes, and that HIF-1 alpha is not directly involved in regulation of CYP3A4 or CYP3A7 expression.