Human CYP1A1GFP Expression in Transgenic Mice Serves as a Biomarker for Environmental Toxicant Exposure

Abstract

The human CYP1A1 gene is regulated by the aryl hydrocarbon receptor (AhR), and induction of CYP1A1 is known to play an important role in xenobiotic metabolism. To examine the regulation of human CYP1A1 in vivo, we created a transgenic mouse strain (Tg-CYP1A1(GFP)) expressing a chimeric gene consisting of the entire human CYP1A1 gene (15 kb) fused with a GFP reporter gene. The treatment of Tg-CYP1A1(GFP) mice with a single intraperitoneal dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or benzo[a]pyrene (B[a]P) led to the induction of CYP1A1(GFP) in both the liver and the lung as determined by fluorescence and Western blot analysis. The localization of induced fluorescence in liver also demonstrated the usefulness of cultured hepatocytes in examining the actions of AhR agonists toward induction of CYP1A1(GFP). Other routes of B[a]P administration, such as by oral exposure at 100 mg/kg for 3 days, led to reduced induction of CYP1A1(GFP) in liver and lung. In liver, expression of CYP1A1(GFP) was a sensitive marker for oral exposure, while mouse CYP1A1 was not induced at these doses. While first pass metabolism of B[a]P in the gastrointestinal tract reduces the potential of the AhR to induce CYP1A1(GFP) in the liver, adequate concentrations reach the hepatic circulation as demonstrated by induction of human UGT1A proteins in transgenic mice that express the human UGT1 locus. The capability to identify fluorescently labeled CYP1A1 in vivo provides a sensitive measurement of gene response and links exposure to potential environmental toxicants and activation of the AhR.

Persistent induction of cytochrome P450 (CYP)1A enzymes by 3-methylcholanthrene in vivo in mice is mediated by sustained transcriptional activation of the corresponding promoters

“…The observation that MC elicited greater degree induction of luciferase expression in the CYP1A1-luc mice compared to that of CYP1A2-luc mice was consistent with the previous reports from other laboratories [28,29] including our own [7] that PAHs induce CYP1A1 to a greater extent than CYP1A2. In fact, our observations in this study show for the first time that persistent transcriptional activation of the CYP1A promoters occurs in vivo .…”

Augmented oxygen-mediated transcriptional activation of cytochrome P450 (CYP)1A expression and increased susceptibilities to hyperoxic lung injury in transgenic mice carrying the human CYP1A1 or mouse 1A2 promoter in vivo

“…The fact that hyperoxia induced the endogenous CYP1A1 and 1A2 activities in the transgenic mice suggests that introduction of the promoters into the mice did not affect the phenomenon of induction, and that the molecular properties governing gene expression of the CYP1A-luc mice and the endogenous CYP1A genes are similar [31–33]. …”

Responses of Synechocystis sp. PCC 6803 (cyanobacterium) photosystem II to pyrene stress

“…E-mail: reli@ihb.ac.cn in detection and evaluation of various stresses on plant (Pinior et al, 2005;Strauss et al, 2006;Christen et al, 2007) and cyanobacteria (Lu and Vonshak, 1999;Bueno et al, 2004;Zhao et al, 2008). Recently, molecular responses such as changes in gene expression have been detected to assess the biological effect of toxic chemicals on microbial organisms (Nadeau et al, 2001;De Jong et al, 2006;Operaña et al, 2007). The cyanobacterium Synechocystis sp.…”