The common indoor air pollutant α-pinene is metabolised to a genotoxic metabolite α-pinene oxide

Abstract

1. α-Pinene caused a concentration-responsive increase in bladder hyperplasia and decrease in sperm counts in rodents following inhalation exposure. Additionally, it formed a prospective reactive metabolite, α-pinene oxide.

2. To provide human relevant context for data generated in animal models and explore potential mechanism, we undertook studies to investigate the metabolism of α-pinene to α-pinene oxide and mutagenicity of α-pinene and α-pinene oxide.

3. α-Pinene oxide was formed in rat and human microsomes and hepatocytes with some species differences. Based on area under the concentration versus time curves, the formation of α-pinene oxide was up to 4-fold higher in rats than in humans.

4. While rat microsomes cleared α-pinene oxide faster than human microsomes, the clearance of α-pinene oxide in hepatocytes was similar between species.

5. α-Pinene was not mutagenic with or without induced rat liver S9 in Salmonella typhimurium or Escherichia coli when tested up to 10 000 µg/plate while α-pinene oxide was mutagenic at ≥25 µg/plate.

6. α-Pinene was metabolised to α-pinene oxide under the conditions of the bacterial mutation assay although the concentration was approximately 3-fold lower than the lowest α-pinene oxide concentration that was positive in the assay, potentially explaining the lack of mutagenicity observed with α-pinene.

Keywords:

• α-pinene
• α-pinene oxide
• metabolism
• hepatocytes
• monoterpene
• bacterial mutagenicity

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Correction

Correction Statement

This article was originally published with errors, which have now been corrected in the online version. Please see Correction (http://dx.doi.org/10.1080/00498254.2022.2154946)

Acknowledgements

The authors are grateful to Drs Pei-Li Yao and Sreenivasa Ramaiahgari for their review of this manuscript. This work was supported by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences, Intramural Research project ZIA ES103316-05, and performed for the Division National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, U.S. Department of Health and Human Services, under contracts HHSN273201400022C (RTI International, RTP, NC) and HHSN273201300009C (Integrated Laboratory Systems, RTP, NC).

Disclosure statement

No potential conflict of interest was reported by the author(s).