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Application of Genetically Encoded Fluorescent Nitric Oxide (NO•) Probes, the geNOps, for Real-time Imaging of NO• Signals in Single Cells
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Application of Genetically Encoded Fluorescent Nitric Oxide (NO•) Probes, the geNOps, for Real-time Imaging of NO• Signals in Single Cells

Published on: March 16, 2017

Contribution of hepatocyte nuclear factor-4 to down-regulation of CYP2D6 gene expression by nitric oxide

Hirokazu Hara1, Tetsuo Adachi

  • 1Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, Gifu, Japan. harah@gifu-pu.ac.jp

Molecular Pharmacology
|December 26, 2001
PubMed

Insights

Nitric oxide (NO) suppresses CYP2D6 gene expression transcriptionally. This occurs by NO directly inhibiting hepatocyte nuclear factor-4 (HNF4) binding to the CYP2D6 promoter, independent of guanylate cyclase.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Pharmacology

Background:

  • Nitric oxide (NO) is involved in inflammatory and infectious conditions.
  • NO is known to down-regulate cytochrome P450 genes, but the mechanism is unclear.

Purpose of the Study:

  • To elucidate the mechanism by which NO down-regulates CYP2D6 gene expression.
  • To investigate the role of NO in the transcriptional regulation of CYP2D6.

Main Methods:

  • Used HepG2 cells and NO donors (NOR4, GSNO) to study CYP2D6 expression.
  • Utilized CYP2D6 promoter-luciferase constructs and deletion analysis.
  • Performed electrophoretic mobility-shift assays and site-directed mutagenesis to assess HNF4 binding.

Main Results:

  • NO donors decreased CYP2D6 mRNA and promoter activity in a concentration-dependent manner.
  • Suppression of CYP2D6 promoter activity by NO was independent of guanylate cyclase.
  • The -80 to +65 region of the CYP2D6 promoter, containing the HNF4 binding site, was crucial for NO-mediated suppression.
  • NO directly inhibited HNF4 DNA-binding activity.

Conclusions:

  • NO down-regulates CYP2D6 gene expression at the transcriptional level.
  • This regulation is mediated, in part, by the direct inhibition of HNF4 binding to the CYP2D6 promoter via an NO-guanylate cyclase-independent pathway.

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