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  3. Metabolism-dependent mutagenicity of two structurally similar tobacco-specific nitrosamines (N-nitrosonornicotine and N-nitrosoanabasine) in human cells, partially different CYPs being activating enzymes

Metabolism-dependent mutagenicity of two structurally similar tobacco-specific nitrosamines (N-nitrosonornicotine and N-nitrosoanabasine) in human cells, partially different CYPs being activating enzymes

  • Toxicology. 2024 Mar 13:504:153774. doi: 10.1016/j.tox.2024.153774.
Yijing Chen 1,  Zongying Yang 2,  Zhao Zhou 1,  Ellery J Liu 3,  Wenwen Luo 1,  Zhini He 4,  Weili Han 5,  Yungang Liu 6
Affiliations

Affiliations

  • 1 Department of Toxicology, School of Public Health (Guangdong Provincial Key Laboratory of Tropical Disease Research), Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China.
  • 2 Department of Toxicology, School of Public Health (Guangdong Provincial Key Laboratory of Tropical Disease Research), Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China; School of Clinical Technology, Sichuan Vocational College of Health and Rehabilitation, 3 Deming Road, Zigong, Sichuan Province 643000, China.
  • 3 International High School Section, Guangzhou Experimental Foreign Language School, 599 Guanghuayi Road, Guangzhou 510440, China.
  • 4 Research Center of Food Safety and Health, School of Public Health (Guangdong Provincial Key Laboratory of Tropical Disease Research), Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China.
  • 5 Department of inspection and quarantine, School of Public Health (Guangdong Provincial Key Laboratory of Tropical Disease Research), Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China.
  • 6 Department of Toxicology, School of Public Health (Guangdong Provincial Key Laboratory of Tropical Disease Research), Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China. Electronic address: yungliu@126.com.
PMID: 38490321 DOI: 10.1016/j.tox.2024.153774
Abstract

N-nitrosonornicotine (NNN) and N-nitrosoanabasine (NAB) are both tobacco-specific nitrosamines bearing two heterocyclic amino groups, NAB bearing an extra -CH2- group (conferring a hexa- rather than penta-membered cycle) but with significantly decreased carcinogenicity. However, their activating Enzymes and related mutagenicity remain unclear. In this study, the chemical-CYP interaction was analyzed by molecular docking, thus the binding energies and conformations of NNN for human CYP2A6, 2A13, 2B6, 2E1 and 3A4 appeared appropriate as a substrate, so did NAB for human CYP1B1, 2A6, 2A13 and 2E1. The micronucleus test in human hepatoma (HepG2) cells with each compound (62.5-1000 μM) exposing for 48 h (two-cell cycle) was negative, however, pretreatment with bisphenol AF (0.1-100 nM, CYPs inducer) and ethanol (0.2% v:v, CYP2E1 inducer) potentiated micronucleus formation by both compounds, while CITCO (1 μM, CYP2B6 inducer) selectively potentiated that by NNN. In C3A cells (endogenous CYPs enhanced over HepG2) both compounds induced micronucleus, which was abolished by 1-aminobenzotriazole (60 μM, CYPs inhibitor) while unaffected by 8-methoxypsoralen (1 μM, CYP2A inhibitor). Consistently, NNN and NAB induced micronucleus in V79-derived recombinant cell lines expressing human CYP2B6/2E1 and CYP1B1/2E1, respectively, while negative in those expressing other CYPs. By immunofluorescent assay both compounds selectively induced centromere-free micronucleus in C3A cells. In PIG-A assays in HepG2 cells NNN and NAB were weakly positive and simply negative, respectively; however, in C3A cells both compounds significantly induced gene mutations, NNN being slight more potent. Conclusively, both NNN and NAB are mutagenic and clastogenic, depending on metabolic activation by partially different CYP Enzymes.

Keywords

Centromere protein B; Clastogenicity; Metabolic activation; Micronuclei; Tobacco-specific nitrosamines.

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