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Updated: Aug 2, 2026
An Air-liquid Interface Bronchial Epithelial Model for Realistic, Repeated Inhalation Exposure to Airborne Particles for Toxicity Testing
Published on: May 13, 2020
Oxidative interactions of synthetic lung epithelial lining fluid with metal-containing particulate matter
1Curriculum in Toxicology, The University of North Carolina at Chapel Hill, 27599, USA.
Abstract:
Epidemiology studies show association of morbidity and mortality with exposure to ambient air particulate matter (PM). Metals present in PM may catalyze oxidation of important lipids and proteins present in the lining of the respiratory tract. The present study investigated the PM-induced oxidation of human bronchoalveolar lavage (BAL) fluid (BALF) and synthetic lung epithelial lining fluid (sELF) through the measurement of oxygen incorporation and antioxidant depletion assays. Residual oil fly ash (ROFA), an emission source PM that contains approximately 10% by weight of soluble transition metals, was added (0-200 microg/ml) to BALF or sELF and exposed to 20% (18)O(2) (24 degrees C, 4 h). Oxygen incorporation was quantified as excess (18)O in the dried samples after incubation. BALF and diluted sELF yielded similar results. Oxygen incorporation was increased by ROFA addition and was enhanced by ascorbic acid (AA) and mixtures of AA and glutathione (GSH). AA depletion, but not depletion of GSH or uric acid, occurred in parallel with oxygen incorporation. AA became inhibitory to oxygen incorporation when it was present in high enough concentrations that it was not depleted by ROFA. Physiological and higher concentrations of catalase, superoxide dismutase, and glutathione peroxidase had no effect on oxygen incorporation. Both protein and lipid were found to be targets for oxygen incorporation; however, lipid appeared to be necessary for protein oxygen incorporation to occur. Based on these findings, we predict that ROFA would initiate significant oxidation of lung lining fluids after in vivo exposure and that AA, GSH, and lipid concentrations of these fluids are important determinants of this oxidation.
Insights
Exposure to air particulate matter (PM) causes lung lining fluid oxidation. Residual oil fly ash (ROFA) increased oxidation, with ascorbic acid (AA) and lipids playing key roles in this process.
Area of Science:
- Environmental Health
- Toxicology
- Biochemistry
Background:
- Epidemiological studies link ambient particulate matter (PM) exposure to increased morbidity and mortality.
- Metals in PM can catalyze oxidation of lipids and proteins in the respiratory tract lining.
- Understanding PM-induced oxidative stress in lung fluids is crucial for respiratory health.
Purpose of the Study:
- To investigate the oxidative effects of PM on human bronchoalveolar lavage (BAL) fluid and synthetic lung epithelial lining fluid (sELF).
- To quantify oxygen incorporation and antioxidant depletion in response to PM exposure.
- To identify key components influencing PM-induced lung fluid oxidation.
Main Methods:
- Incubation of BALF and sELF with residual oil fly ash (ROFA) under an 18O2 atmosphere.
- Quantification of oxygen incorporation using excess 18O measurements.
- Assays for antioxidant depletion (ascorbic acid, glutathione, uric acid) and enzyme activity.
Main Results:
- ROFA exposure significantly increased oxygen incorporation into BALF and sELF.
- Ascorbic acid (AA) enhanced ROFA-induced oxidation, and its depletion correlated with oxygen incorporation.
- Lipids were necessary for protein oxidation, suggesting a multi-component oxidative cascade.
Conclusions:
- Residual oil fly ash (ROFA) initiates significant oxidation of lung lining fluids.
- Ascorbic acid (AA), glutathione (GSH), and lipid concentrations are critical determinants of PM-induced lung fluid oxidation.
- These findings highlight the potential for PM to cause oxidative damage in the respiratory tract.
