Am. J. Respir. Cell Mol. Biol.,
Volume 21, Number 2, August, 1999 177-184
Cis-Acting Sequences from the Rat Cytochrome P450 2B1 Gene Confer
Pulmonary and Phenobarbital-Inducible Expression in Transgenic Mice
Tobias
Skarin,
Rune
Becher,
Anders
Bucht,
Kristina
Duvefelt,
Staffan
Bohm,
Toril
Ranneberg-Nilsen,
Edel Marie
Lilleaas,
Per Everhard
Schwarze,
and
Rune
Toftgård
Department of Biosciences and Center for Nutrition and Toxicology, Karolinska Institute, Huddinge; Department of
Medicine, Unit of Rheumatology, Karolinska Hospital, Karolinska Institute, Stockholm; Department of Cell
and Molecular Biology, University of Umeå, Umeå; Department of Molecular Sciences, Astra Arcus AB,
Södertälje, Sweden; Department of Environmental Medicine, National Institute of Public Health;
and Institute of Microbiology, The National Hospital, Oslo, Norway.
Specific cytochrome P450 enzymes show tissue-specific induction, and different regulatory units for expression of these enzymes have been identified. The regulation of the phenobarbital (PB)-inducible P450
genes has been relatively well characterized in terms of PB induction, but less so with regard to tissue-specific expression. CYP2B2 is not expressed in the rat lung, whereas cytochrome P450 2B1 (CYP2B1) is a
dominating enzyme in the same tissue. The constitutive expression of CYP2B1 and CYP2B2 in liver is
low, but inducible by PB, whereas the pulmonary expression of CYP2B1 is not induced by PB. This indicates utilization of different regulating mechanisms in the two organs. A gene construct consisting of the
structural gene for LacZ coupled to a 1.3-kb 5' fragment of the rat CYP2B1 gene was used to generate
transgenic mice in order to further elucidate the mechanism behind tissue-specific expression and PB induction of the CYP2B1 gene. Using reverse transcriptase-polymerase chain reaction on total RNA extracted from lung and liver tissue, a lung-specific transcription of the transgene was observed. Transcription of the construct was also observed in livers from PB-treated transgenic animals. By histochemical
staining of lung sections with 5-bromo-4-chloro-3-indolyl-
-D-galactopyranoside (X-gal), we demonstrated expression at the protein level in bronchiolar cells. In conclusion, our results revealed that the region extending to 
1.3 kb in the 5' flanking region of the CYP2B1 gene included sequences that could
partly account for the lung-specific transcription of CYP2B1 and the hepatic induction of CYP2B1 transcription by PB.
