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Circadian oscillator NPAS2 regulates diurnal expression and activity of CYP1A2 in mouse liver

Yiting He1, Haobin Cen2, Lianxia Guo2

  • 1Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, China.

Biochemical Pharmacology
|November 15, 2022
PubMed

Insights

The study found that NPAS2 controls the daily rhythm of hepatic CYP1A2 expression and activity in mice. This discovery enhances understanding of circadian metabolism and drug effectiveness over time.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Chronobiology

Background:

  • Hepatic cytochrome P450 enzymes, including CYP1A2, exhibit diurnal variations influencing drug metabolism.
  • The molecular mechanisms regulating the circadian expression of CYP1A2 are not fully understood.
  • NPAS2 (Neuronal PAS domain-containing protein 2) is a transcription factor involved in circadian rhythm regulation.

Purpose of the Study:

  • To investigate the role of NPAS2 in regulating the diurnal expression and activity of hepatic CYP1A2.
  • To elucidate the underlying molecular mechanisms of NPAS2-mediated regulation of CYP1A2.
  • To assess the impact of NPAS2 on CYP1A2 rhythmicity and enzymatic function.

Main Methods:

  • Utilized Npas2 knockout mice and liver cell lines (AML-12, Hepa1-6, HepG2) to study NPAS2 function.
  • Quantified mRNA and protein levels of CYP1A2 using RT-qPCR and Western blotting.
  • Assessed in vitro and in vivo CYP1A2 activity using phenacetin and theophylline.
  • Investigated transcriptional regulation via luciferase reporter assays and ChIP-Seq analysis.

Main Results:

  • Loss of Npas2 in mice significantly decreased CYP1A2 mRNA and protein levels in the liver.
  • Npas2 ablation abolished the diurnal rhythmicity of hepatic CYP1A2 expression and activity.
  • NPAS2 directly binds to an E-box-like element in the Cyp1a2 promoter, acting as a positive transcriptional regulator.
  • Cell-based assays confirmed NPAS2's positive regulatory effect on CYP1A2 expression.

Conclusions:

  • NPAS2 is a critical transcriptional regulator of diurnal CYP1A2 expression and activity in the mouse liver.
  • These findings provide insights into the molecular basis of circadian control over drug-metabolizing enzymes.
  • Understanding NPAS2-CYP1A2 interactions has implications for chronopharmacokinetics and personalized medicine.
Keywords:
CYP1A2ChronopharmacokineticsCircadian rhythmNPAS2Transcriptional activation

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