title: In vivo effects of the pure aryl hydrocarbon receptor antagonist GNF-351 after oral administration are limited to the gastrointestinal tract.
abstract: OBJECTIVE
  GNF-351 is a potent aryl hydrocarbon receptor (AHR) antagonist that inhibits dioxin response element-dependent and independent activities. Here, the absorption, metabolism and in vivo AHR antagonist activity of GNF-351 were investigated.
  
  
  METHODS
  LC-MS metabolomics was used to analyse GNF-351 metabolism in vitro and in vivo. Recombinant drug-metabolizing enzymes were employed to determine the enzymes involved in GNF-351 metabolism. Analysis of target AHR genes was performed to investigate the inhibitory effects of GNF-351 towards AHR activation.
  
  
  RESULTS
  Several phase I metabolites were generated after GNF-351 was incubated with microsomes from human or mouse liver and intestine, including two oxidized GNF-351 and one tri-demethylated GNF-351. Poor absorption from the intestine resulted in no detectable levels of GNF-351 in mouse serum (0-6 h) and urine (24 h) and almost all GNF-351 was found in the faeces after 24 h. Analysis of faeces further revealed all the in vitro phase I metabolites. Novel metabolites were detected, including one di-oxidized GNF-351, two oxidized and tri-demethylated GNF-351, one dehydrogenated product of oxidized GNF-351, and one sulfation product of di-oxidized GNF-351. Cytochromes P450 were demonstrated to be the major enzymes involved in metabolism of GNF-351. After oral administration to mice, GNF-351 readily inhibited β-naphthoflavone-induced AHR activation in ileum and colon, but not that in the liver.
  
  
  CONCLUSIONS
  While poor absorption and extensive metabolism after oral administration limited the in vivo effects of the pure AHR antagonist GNF-351 in liver, it could be used to inhibit AHR activation in intestine and colon.
authors.affiliation: Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Zhong-Ze
authors.initials: ZZ
authors.lastname: Fang
authors.forename: Kristopher W
authors.initials: KW
authors.lastname: Krausz
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Nagaoka
authors.forename: Naoki
authors.initials: N
authors.lastname: Tanaka
authors.forename: Krishne
authors.initials: K
authors.lastname: Gowda
authors.forename: Shantu G
authors.initials: SG
authors.lastname: Amin
authors.forename: Gary H
authors.initials: GH
authors.lastname: Perdew
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Gonzalez
mesh_terms: D000284:Administration, Oral; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D001682:Biological Availability; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D005243:Feces / Q000737:chemistry; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D008297:Male; D055432:Metabolomics / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D011687:Purines / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors* / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D007211:Indoles; D011687:Purines; D018336:Receptors, Aryl Hydrocarbon; C111235:AHR protein, human; C484722:Ahr protein, mouse; C560625:N-(2-(3H-indol-3-yl)ethyl)-9-isopropyl-2-(5-methyl-3-pyridyl)purin-6-amine
keywords: AHR antagonist; GNF-351; absorption; metabolic map