Induction of the drug metabolizing enzyme CYP2D in monkey brain by chronic nicotine treatment

Amandeep Mann, Sharon Miksys, Anna Lee, Deborah C. Mash, Rachel F. Tyndale

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61 Scopus citations

Abstract

Cytochrome P450 (CYP) 2D6, an enzyme found in the liver and the brain, is involved in the metabolism of numerous centrally acting drugs (e.g. antidepressants, neuroleptics, opiates), endogenous neurochemicals (e.g. catecholamines) and in the inactivation of neurotoxins (e.g. pesticides, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)). Although CYP2D6 is essentially an uninducible enzyme in the liver, we show that smokers have higher CYP2D6 in the brain, especially in the basal ganglia. In order to determine whether nicotine, a component of cigarette smoke, could increase brain CYP2D, African Green monkeys were treated chronically with nicotine (0.05 mg/kg for 2 days, then 0.15 mg/kg for 2 days followed by 0.3 mg/kg for 18 days s.c., b.i.d.). Monkeys treated with nicotine showed significant induction of CYP2D in brain when compared to saline-treated animals as detected by western blotting and immunocytochemistry. No changes in liver CYP2D were observed in nicotine-treated monkeys. Induction was observed in various brain regions including those affected in Parkinson's disease (PD) such as substantia nigra (3-fold, p = 0.01), putamen (2.1-fold, p = 0.001) and brainstem (2.4-fold, p = 0.001), with the caudate nucleus approaching significance (1.6-fold, p = 0.07). Immunocytochemistry revealed that the expression of CYP2D in both saline- and nicotine-treated monkeys is cell-specific particularly in the cerebellum, frontal cortex and hippocampus. These results suggest that monkey brain expresses CYP2D, which is induced in specific cells and brain regions upon chronic nicotine treatment. Smokers, or those using nicotine treatment, may have higher levels of brain CYP2D6 that may result in altered localized CNS drug metabolism and inactivation of neurotoxins.

Original languageEnglish (US)
Pages (from-to)1147-1155
Number of pages9
JournalNeuropharmacology
Volume55
Issue number7
DOIs
StatePublished - Dec 2008

Bibliographical note

Funding Information:
Funding for this work was provided by the Centre for Addiction and Mental Health, CIHR Grant (MOP14173) and a Canada Research Chair in Pharmacogenetics to Dr R.F. Tyndale. Additional support was provided by CIHR Tobacco Use in Special Populations Fellowship to A. Mann. Dr. R.F. Tyndale has shares in Nicogen Research Inc. Funds were not received from Nicogen for these studies, nor was this manuscript reviewed by individuals associated with Nicogen. We would like to thank Dr. Roberta Palmour for assistance with the experiments and Ewa Hoffmann for genotyping the human brains.

Keywords

  • Brain drug metabolism
  • CYP2D6
  • Nicotine
  • Non-human primate
  • Parkinson's disease
  • Smoking

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