Related Experiment Videos
Suppression of CYP1A1 expression by 4-nonylphenol in murine Hepa-1c1c7 cells
1Department of Pharmacy, Chosun University, 375 Seosuk-dong, Gong-ku, 501-759, Kwangju, South Korea. hgjeong@mail.chosun.ac.kr
Abstract:
This study investigated the effects that 4-nonylphenol (NP) has on CYP1A1 expression in Hepa-1c1c7 cell cultures. NP alone did not affect CYP1A1-specific 7-ethoxyresorufin-O-deethylase (EROD) activity. In contrast, the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible EROD activities were markedly reduced upon concomitant treatment with TCDD and NP in a dose-dependent manner. Treatment with tamoxifen, an anti-estrogen that acts through the estrogen receptor, did not affect the suppressive effects that NP has on TCDD-inducible EROD activity. The TCDD-inducible CYP1A1 mRNA levels were markedly suppressed upon concomitant treatment with TCDD and NP that is consistent with their effects on EROD activity. A transient transfection assay using dioxin-response element (DRE)-linked luciferase and an electrophoretic mobility shift assay revealed that NP reduced the transformation of the aryl hydrocarbon (Ah) receptor to a form capable of binding specifically to the DRE sequence of the CYP1A1 gene promoter. These results suggest that the down-regulation of CYP1A1 gene expression by NP in Hepa-1c1c7 cells might be an antagonism of the DRE-binding potential of the nuclear Ah receptor, but is not mediated through the estradiol receptor.
Insights
4-nonylphenol (NP) suppresses 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 gene expression by interfering with the aryl hydrocarbon (Ah) receptor
Area of Science:
- Environmental Toxicology
- Molecular Biology
- Cellular Biology
Background:
- CYP1A1 gene expression is a key indicator of cellular response to environmental contaminants.
- 4-nonylphenol (NP) is an environmental endocrine disruptor with potential effects on cellular pathways.
- The aryl hydrocarbon receptor (AhR) is a critical transcription factor regulating CYP1A1 expression.
Purpose of the Study:
- To investigate the impact of 4-nonylphenol (NP) on CYP1A1 gene expression in Hepa-1c1c7 cells.
- To elucidate the mechanism by which NP affects TCDD-induced CYP1A1 expression.
- To determine if the effects of NP are mediated through the estrogen receptor.
Main Methods:
- Hepa-1c1c7 cell culture treated with NP and TCDD.
- Measurement of 7-ethoxyresorufin-O-deethylase (EROD) activity.
- Analysis of CYP1A1 mRNA levels.
- Transient transfection assays with DRE-luciferase reporter.
- Electrophoretic mobility shift assays (EMSA) for AhR binding.
Main Results:
- NP alone did not affect basal EROD activity.
- NP dose-dependently suppressed TCDD-induced EROD activity and CYP1A1 mRNA levels.
- Tamoxifen treatment did not alter the suppressive effects of NP.
- NP inhibited the transformation of the AhR to a DNA-binding form for the CYP1A1 gene promoter.
Conclusions:
- 4-nonylphenol down-regulates CYP1A1 gene expression in Hepa-1c1c7 cells.
- The mechanism involves antagonism of the DRE-binding potential of the AhR.
- These effects are independent of the estradiol receptor pathway.