Respiratory Impacts of Hazardous Air Pollutants in Allergic Mice: Sex Differences and In Vitro Concordance.

Validation of high-throughput in vitro assessments of hazardous air pollutants (HAPs) and other EPA high-priority chemicals requires testing in animal models to demonstrate in vitro predictive ability. Acrolein (ACR) and trichloroethylene (TCE) are among several HAPs designated as high priority chemicals within the U.S. EPA Toxic Substances Control Act inventory, and may exacerbate respiratory symptoms in susceptible populations such as asthmatics. Here we evaluated real-time pulmonary responses to ACR and TCE in control and house dust mite (HDM)-allergic male (M) and female (F) mice and subsequent inflammatory biomarkers. On two consecutive days, mice were exposed nose-only in head-out plethysmographs to air (20 min) followed by increasing concentrations (25 min each) of ACR (0.1, 0.32, 1.0, 3.2 ppm) or TCE (3.2, 10, 31.6, 100 ppm), corresponding to ongoing in vitro assessments. Separate groups were exposed to air only for comparison of inflammatory responses. Breathing frequency significantly declined in both M and F HDM-allergic groups at 1.0 ppm ACR on both exposure days (group means 19-30% lower than air control) and was sharply lower (39-67%) at 3.2 ppm ACR, while TCE (10-100 ppm) also significantly reduced frequency, though to a lesser extent (12-23%). M mice had higher baseline frequency than F, which declined to a greater extent with increasing ACR concentration. Other parameters of respiratory timing, flows, and volumes indicated overall greater effects of ACR and TCE in M and allergic groups compared with F and control groups. Four hours after final exposure, HDM-allergic F mice had greater indices of allergic inflammation than M mice (e.g. bronchoalveolar lavage (BAL) eosinophils, lymphocytes, albumin, and IL-5), but relatively few differences with respect to HAPs exposure. TCE-exposed HDM-allergic F mice had greater BAL eosinophils and N-acetyl-glucosaminidase, but lower MIP-2, than ACR-exposed allergic F mice. Effects of ACR and TCE on real-time respiratory physiology correlated reasonably well with cell viability results in BEAS-2B cells (CellTiter Glo viability ATP assay). Assessment of additional HAPs in the allergic mouse model will further determine validity of HAPs effects predicted by high-throughput in vitro assays. (This abstract does not represent U.S. EPA policy.)

Impact/Purpose

In this project, we are examining physiological and biochemical effects of individual HAPs designated as high priority chemicals within the TSCA inventory. The individual chemicals have been selected in coordination with ongoing in vitro studies of these chemicals to assess toxicity and mode of action as determined by genomic effects (J. Zavala and M. Higuchi, Chemical Safety and Sustainability (CSS) Task 3.3, QAPP E-EPHD-0031144-QP-1-0). Four of these chemicals were selected from the 10 TSCA high-priority chemicals recently chosen for risk evaluation (1-bromopropane, trichloroethylene, carbon tetrachloride, and dichloromethane), and four were chosen from other HAPs which have a significant burden on health and the environment (1,3-butadiene, acetaldehyde, formaldehyde, and acrolein). We plan to assess the relative acute toxicity of these eight chemicals and provide a ranking of effects on pulmonary and allergic asthmatic responses in Balb/cJ mice, a strain which is widely used for the assessment of allergic responses. Analysis of lung respiratory function and molecular endpoints will allow us to determine which high-priority environmental chemicals are of greatest concern for exacerbation of allergic airways disease and validate the ongoing in vitro assessments.

Citation

Gavett, S., M. Hargrove, S. Vance, P. Evansky, L. Copeland, R. Grindstaff, J. Dye, J. Zavala, M. Higuchi, AND Matthew Gilmour. Respiratory Impacts of Hazardous Air Pollutants in Allergic Mice: Sex Differences and In Vitro Concordance. Society of Toxicology, Anaheim, CA, March 15 - 19, 2020.