Circadian Regulation of Hepatic Cytochrome P450 2a5 by Peroxisome Proliferator-Activated Receptor γ

Drug Metab Dispos. 2018 Nov;46(11):1538-1545. doi: 10.1124/dmd.118.083071. Epub 2018 Aug 28.

Abstract

Human CYP2A6 (Cyp2a5 in mice) plays an important role in metabolism and detoxification of various drugs and chemicals. Here, we investigated a potential role of peroxisome proliferator-activated receptor γ (Ppar-γ) in circadian regulation of the Cyp2a5 enzyme. We first showed that Cyp2a5 mRNA and protein in mouse liver displayed robust circadian oscillations. Consistent with a circadian protein pattern, Cyp2a5-mediated 7-hydroxylation of coumarin was circadian time-dependent. Formation of 7-hydroxycoumarin was more extensive at a dosing time of Zeitgeber time 2 (ZT2) than that at ZT14. Interestingly, the nuclear receptor Ppar-γ was also a circadian gene. Circadian Ppar-γ protein level was strongly correlated with the Cyp2a5 mRNA level (r = 0.989). Furthermore, Ppar-γ activation (by a selective agonist, rosiglitazone) upregulated Cyp2a5 expression in Hepa-1c1c7 cells, whereas Ppar-γ knockdown downregulated Cyp2a5 expression. Also, Ppar-γ knockdown blunted the rhythmicity of Cyp2a5 mRNA in serum-shocked Hepa-1c1c7 cells. In addition, a combination of promoter truncation analysis, mobility shift, and chromatin immunoprecipitation assays revealed that Ppar-γ directly bound to a PPAR response element (i.e., the -1418- to -1396-bp region) within Cyp2a5 promoter and activated the gene transcription. Taken together, Ppar-γ was a transcriptional activator of Cyp2a5, and its rhythmic expression contributed to circadian expression of Cyp2a5.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aryl Hydrocarbon Hydroxylases / genetics*
  • Cell Line
  • Circadian Clocks / genetics*
  • Cytochrome P450 Family 2 / genetics*
  • Down-Regulation / genetics
  • Gene Expression Regulation, Enzymologic / genetics
  • Hepatocytes / physiology*
  • Humans
  • Liver / physiology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • PPAR gamma / genetics*
  • Promoter Regions, Genetic / genetics
  • RNA, Messenger / genetics
  • Transcription, Genetic / genetics
  • Transcriptional Activation / genetics
  • Up-Regulation / genetics

Substances

  • PPAR gamma
  • RNA, Messenger
  • Aryl Hydrocarbon Hydroxylases
  • Cyp2a5 protein, mouse
  • Cytochrome P450 Family 2