Abstract
Cigarette smoke is known to induce cytochrome P4501A1 expression and activity in a variety of species. Although the elevation of this isozyme is assumed to be associated with the activation of the CYP1A1 gene through a ligand-mediated mechanism involving the Ah-receptor (AhR), this has not been determined. In this study we have examined the mechanism by which an ambient level of aged and diluted sidestream cigarette smoke (ADSS) induces cytochrome P4501A1. Effects of ADSS on C57BL/6N and DBA/2N mice were examined. Induction of P4501A1-associated ethoxyresorufin-O-dealkylase (EROD) activity was observed in the lungs of C57BL/6N mice, while there was no induction in DBA/2N mice. ADSS also induced EROD in wild-type mouse hepatoma (Hepa1c1c7) cells (hepa1), but not in variant hepa1 cells defective in the AhR nuclear translocator (ARNT) protein. ADSS exposure of recombinant hepa1 cells, stably transfected with a reporter plasmid containing the luciferase gene under control of several dioxin responsive enhancers (DREs), resulted in a time- and exposure-dependent induction of luciferase activity. ADSS-mediated induction of luciferase activity was inhibited by α-naphthoflavone (αNF), an Ah-receptor antagonist. Gel retardation analysis demonstrated that exposure to ADSS induced transformation and DNA binding of the AhR complex. In summary, our results not only indicate a role for the AhR in mediating the induction of P4501A1 by ADSS, but also demonstrate that environmentally relevant levels of ADSS must contain AhR ligands at sufficient concentrations to activate gene expression in an AhR-dependent manner.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 76-83 |
| Number of pages | 8 |
| Journal | Toxicology and Applied Pharmacology |
| Volume | 141 |
| Issue number | 1 |
| DOIs | |
| State | Published - Nov 1996 |
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ASJC Scopus subject areas
- Pharmacology
- Toxicology
Cite this
Ah-receptor-dependent modulation of gene expression by aged and diluted sidestream cigarette smoke. / Gebremichael, A.; Tullis, K.; Denison, M. S.; Cheek, J. M.; Pinkerton, Kent E.
In: Toxicology and Applied Pharmacology, Vol. 141, No. 1, 11.1996, p. 76-83.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Ah-receptor-dependent modulation of gene expression by aged and diluted sidestream cigarette smoke
AU - Gebremichael, A.
AU - Tullis, K.
AU - Denison, M. S.
AU - Cheek, J. M.
AU - Pinkerton, Kent E
PY - 1996/11
Y1 - 1996/11
N2 - Cigarette smoke is known to induce cytochrome P4501A1 expression and activity in a variety of species. Although the elevation of this isozyme is assumed to be associated with the activation of the CYP1A1 gene through a ligand-mediated mechanism involving the Ah-receptor (AhR), this has not been determined. In this study we have examined the mechanism by which an ambient level of aged and diluted sidestream cigarette smoke (ADSS) induces cytochrome P4501A1. Effects of ADSS on C57BL/6N and DBA/2N mice were examined. Induction of P4501A1-associated ethoxyresorufin-O-dealkylase (EROD) activity was observed in the lungs of C57BL/6N mice, while there was no induction in DBA/2N mice. ADSS also induced EROD in wild-type mouse hepatoma (Hepa1c1c7) cells (hepa1), but not in variant hepa1 cells defective in the AhR nuclear translocator (ARNT) protein. ADSS exposure of recombinant hepa1 cells, stably transfected with a reporter plasmid containing the luciferase gene under control of several dioxin responsive enhancers (DREs), resulted in a time- and exposure-dependent induction of luciferase activity. ADSS-mediated induction of luciferase activity was inhibited by α-naphthoflavone (αNF), an Ah-receptor antagonist. Gel retardation analysis demonstrated that exposure to ADSS induced transformation and DNA binding of the AhR complex. In summary, our results not only indicate a role for the AhR in mediating the induction of P4501A1 by ADSS, but also demonstrate that environmentally relevant levels of ADSS must contain AhR ligands at sufficient concentrations to activate gene expression in an AhR-dependent manner.
AB - Cigarette smoke is known to induce cytochrome P4501A1 expression and activity in a variety of species. Although the elevation of this isozyme is assumed to be associated with the activation of the CYP1A1 gene through a ligand-mediated mechanism involving the Ah-receptor (AhR), this has not been determined. In this study we have examined the mechanism by which an ambient level of aged and diluted sidestream cigarette smoke (ADSS) induces cytochrome P4501A1. Effects of ADSS on C57BL/6N and DBA/2N mice were examined. Induction of P4501A1-associated ethoxyresorufin-O-dealkylase (EROD) activity was observed in the lungs of C57BL/6N mice, while there was no induction in DBA/2N mice. ADSS also induced EROD in wild-type mouse hepatoma (Hepa1c1c7) cells (hepa1), but not in variant hepa1 cells defective in the AhR nuclear translocator (ARNT) protein. ADSS exposure of recombinant hepa1 cells, stably transfected with a reporter plasmid containing the luciferase gene under control of several dioxin responsive enhancers (DREs), resulted in a time- and exposure-dependent induction of luciferase activity. ADSS-mediated induction of luciferase activity was inhibited by α-naphthoflavone (αNF), an Ah-receptor antagonist. Gel retardation analysis demonstrated that exposure to ADSS induced transformation and DNA binding of the AhR complex. In summary, our results not only indicate a role for the AhR in mediating the induction of P4501A1 by ADSS, but also demonstrate that environmentally relevant levels of ADSS must contain AhR ligands at sufficient concentrations to activate gene expression in an AhR-dependent manner.
UR - http://www.scopus.com/inward/record.url?scp=0030296896&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030296896&partnerID=8YFLogxK
U2 - 10.1006/taap.1996.0262
DO - 10.1006/taap.1996.0262
M3 - Article
C2 - 8917678
AN - SCOPUS:0030296896
VL - 141
SP - 76
EP - 83
JO - Toxicology and Applied Pharmacology
JF - Toxicology and Applied Pharmacology
SN - 0041-008X
IS - 1
ER -