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A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
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A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s

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Nitrosamines as nicotinic receptor ligands

Hildegard M Schuller1

  • 1Experimental Oncology Laboratory, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA. hmsch@utk.edu

Life Sciences
|April 27, 2007
PubMed

Insights

Nitrosamines like NNK, found in tobacco, activate alpha7 nicotinic acetylcholine receptors (alpha7nAChRs), driving lung cancer cell growth. Green tea and theophylline may prevent this cancer development.

Area of Science:

  • Oncology
  • Pharmacology
  • Toxicology

Background:

  • Nitrosamines, including NNK and NNN derived from nicotine, are carcinogens formed in the body.
  • These compounds and their metabolites can cause genotoxic effects through DNA adduct formation.
  • The alpha7 nicotinic acetylcholine receptor (alpha7nAChR) is implicated in cellular processes relevant to cancer.

Purpose of the Study:

  • To investigate the interaction of nitrosamines with nicotinic acetylcholine receptors.
  • To elucidate the role of alpha7nAChR in the development of small cell lung cancer (SCLC).
  • To explore potential preventative strategies against NNK-induced lung tumorigenesis.

Main Methods:

  • Assessed binding affinities of NNK, NNN, and DEN to alpha7nAChR and other nAChRs.
  • Examined alpha7nAChR expression and downstream signaling pathways (Ca2+, PKC, Raf-1, ERK1/2, c-myc) in SCLC and pulmonary neuroendocrine cells (PNECs).
  • Utilized a hamster model of pulmonary fibrosis and lung cancer induction, with interventions including green tea and theophylline.

Main Results:

  • NNK demonstrated high affinity for alpha7nAChR, while NNN bound to epibatidine-sensitive nAChRs.
  • Exposure to NNK or nicotine increased alpha7nAChR expression and stimulated proliferation in SCLC/PNECs, particularly under elevated CO2 conditions.
  • NNK, DEN, or nicotine induced SCLC-like tumors in hamsters; green tea and theophylline inhibited NNK-induced tumor development and proliferation.

Conclusions:

  • NNK acts as a potent agonist for alpha7nAChR, driving cell proliferation crucial for SCLC development.
  • The alpha7nAChR/RAF/ERK1/2 pathway is a key target for SCLC development in smokers.
  • Green tea and theophylline show potential as preventative agents against nitrosamine-induced lung cancer.

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