A general method for detecting nitrosamide formation in the in vitro metabolism of nitrosamines by cytochrome P450s

Erik S. Carlson, Pramod Upadhyaya, Stephen S Hecht

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

N-nitrosamines are a well-established group of environmental carcinogens, which require cytochrome P450 oxidation to exhibit activity. The accepted mechanism of metabolic activation involves formation of α-hydroxynitrosamines that spontaneously decompose to DNA alkylating agents. Accumulation of DNA damage and the resulting mutations can ultimately lead to cancer. New evidence indicates that α- hydroxynitrosamines can be further oxidized to nitrosamides processively by cytochrome P450s. Because nitrosamides are generally more stable than α-hydroxynitrosamines and can also alkylate DNA, nitrosamides may play a role in carcinogenesis. In this report, we describe a general protocol for evaluating nitrosamide production from in vitro cytochrome P450-catalyzed metabolism of nitrosamines. This protocol utilizes a general approach to the synthesis of the relevant nitrosamides and an in vitro cytochrome P450 metabolism assay using liquid chromatography-nanospray ionization-high resolution tandem mass spectrometry for detection. This method detected N′-nitrosonorcotinine as a minor metabolite of N′-nitrosonornicotine in the example study. The method has high sensitivity and selectively due to accurate mass detection. Application of this method to a wide variety of nitrosamine-cytochrome P450 systems will help determine the generality of this transformation. Because cytochrome P450s are polymorphic and vary in activity, a better understanding of nitrosamide formation could aid in individual cancer risk assessment.

Original languageEnglish (US)
Article numbere56312
JournalJournal of Visualized Experiments
Volume2017
Issue number127
DOIs
StatePublished - Sep 25 2017

    Fingerprint

Keywords

  • Carcinogenesis
  • Cellular biology
  • Cytochrome P450 metabolism
  • Highresolution mass spectrometry
  • Issue 127
  • Nitrosamide
  • Nitrosamine
  • Processive oxidation

Cite this