The Journal of Toxicological Sciences
Online ISSN : 1880-3989
Print ISSN : 0388-1350
ISSN-L : 0388-1350
Original Article
Induction of human cytochrome P450 3A enzymes in cultured placental cells by thalidomide and relevance to bioactivation and toxicity
Norie MurayamaYasuhiro KazukiDaisuke SatohKazuya ArataTasuku HaradaNorio ShibataF. Peter GuengerichHiroshi Yamazaki
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JOURNALS FREE ACCESS

2017 Volume 42 Issue 3 Pages 343-348

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Abstract

Evidence has been presented for auto-induced human cytochrome P450 3A enzyme involvement in the teratogenicity and clinical outcome of thalidomide due to oxidation to 5-hydroxythalidomide and subsequent metabolic activation in livers. In this study, more relevant human placenta preparations and placental BeWo cells showed low but detectable P450 3A4/5 mRNA expression and drug oxidation activities. Human placental microsomal fractions from three subjects showed detectable midazolam 1´- and 4-hydroxylation and thalidomide 5-hydroxylation activities. Human placental BeWo cells, cultured in the recommended media, also indicated detectable midazolam 1´- and 4-hydroxylation and thalidomide 5-hydroxylation activities. To reduce any masking effects by endogenous hormones used in the recommended media, induction of P450 3A4/5 mRNA and oxidation activities were measured in placental BeWo cells cultured with a modified medium containing 5% charcoal-stripped fetal bovine serum. Thalidomide significantly induced P450 3A4/5, 2B6, and pregnane X receptor (PXR) mRNA levels 2 to 3-fold, but rifampicin only enhanced P450 3A5 and PXR mRNA under the modified media conditions. Under these modified conditions, thalidomide also significantly induced midazolam 1´-hydroxylation and thalidomide 5-hydroxylaion activities 3-fold but not bupropion hydroxylation activity. Taken together, activation of thalidomide to 5-hydroxythalidomide with autoinduction of P450 3A enzymes in human placentas, as well as livers, is suggested in vivo.

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© 2017 The Japanese Society of Toxicology
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