LC-MS-based lipidomics to examine acute rat pulmonary responses after nano- and fine-sized ZnO particle inhalation exposure

Abstract

Zinc oxide (ZnO) nano- and fine-sized particles are associated with respiratory toxicity in humans, but the underlying molecular mechanisms remain unclear. Our previous nuclear magnetic resonance-based metabolomic study demonstrated that changes in phosphorylcholine-containing lipids (PC-CLs) in the respiratory system were associated with ZnO particle-induced respiratory toxicity. However, the details of the lipid species associated with adverse effects and possible biomarker signatures have not been identified. Thus, a liquid chromatography-mass spectrometry (LC-MS)-based lipidomics platform was applied to examine the alterations of PC-CL species in the lungs of rats treated with a series of concentrations of nano-sized (35 nm) or fine-sized (250 nm) ZnO particles via inhalation. Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and the Mann–Whitney U (MWU) test with false discovery rate (FDR) control were conducted to explore the perturbed lipid species and to discriminate a potential pulmonary biomarker signature after ZnO particle exposure. The PCA and PLS-DA models revealed that the fine-sized ZnO particle-treated groups and the high-concentration nano-sized group were separated from the control groups as well as from the low and moderate nano-sized groups. The results from the MWU test further suggested that after FDR adjustment, numerous PC-CL species were altered in the high-concentration and moderate-concentration fine-sized groups. Furthermore, our results suggested that lipids involved in anti-oxidation, membrane conformation, and cellular signal transduction were altered in response to ZnO-induced oxidative stress and inflammation. One lipid, PC(18:0/18:1), exhibited good performance (AUC > 0.8) of discriminative ability in distinguishing ZnO particle exposure from the control. These findings not only provide a foundation for the exploration of possible ZnO particle-mediated mechanisms but also suggest a lipid biomarker for ZnO particle exposure.

Keywords:

• Zinc oxide
• nano- and fine-sized particles
• toxicity
• lipidomics
• mass spectrometry
• phosphorylcholine-containing lipids
• phosphatidylcholines
• sphingomyelins

Acknowledgements

The authors thank Ms. M. Ho for assistance with animal experiments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was funded by the Ministry of Science and Technology [MST 96-2621-Z-002-016, MST 97-2621-M-002-008, MST 102-2628-B-002-048-MY3, MST 105-2628-B-002-026-MY3, MST 105-2314-B-002-030, and MST 106-2314-B-002-040] in Taiwan.