Dose-Dependent Respiratory Impacts of Acrolein and TCE in Allergic Mice and Validation of In Vitro Effects

Animal models support validation of high-throughput in vitro assessments of hazardous air pollutants (HAPs) and other methodologically challenging chemicals. Acrolein (ACR) and trichloroethylene (TCE) are EPA high priority HAPs which may exacerbate respiratory symptoms in susceptible populations such as asthmatics. We evaluated real-time pulmonary responses to ACR and TCE in control and house dust mite (HDM)-allergic male (M) and female (F) Balb/cJ mice and subsequent inflammatory biomarkers using 2 protocols with different concentration x time (C x T) exposures. On 2 consecutive days, mice were exposed nose-only in head-out plethysmographs to air followed by increasing concentrations of ACR (0.1, 0.32, 1.0, 3.2 ppm) or TCE (3.2, 10, 32, 100 ppm), corresponding to ongoing in vitro assessments. In protocol 1 (P1), exposures were 25 min at each concentration of ACR or TCE; in protocol 2 (P2) exposures were 7.5 min at the first 3 concentrations and 90 min at the highest concentration; total C x T was 2.6-fold higher in P2. Separate groups were exposed to air only to compare inflammatory responses. Baseline breathing frequency was higher in M vs. F mice; frequency significantly declined in all groups at 3.2 ppm ACR in either P1 or P2 (group means 37-67% lower than air baseline). ACR P1 reduced frequency to a greater extent in M mice, while reductions with P2 were equivalent in both sexes. TCE P1 and P2 (10-100 ppm) also significantly reduced frequency, though to a lesser extent (12-23%). 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 using either protocol. Four hours after final exposure, HDM-allergic F mice had greater indices of allergic inflammation than M mice (bronchoalveolar lavage eosinophils, lymphocytes, albumin, IL-5), but relatively few differences with respect to HAPs exposure, even with higher C x T in P2. 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. We plan to assess the relative acute toxicity of eight chemicals (1-bromopropane, trichloroethylene, carbon tetrachloride, dichloromethane, 1,3-butadiene, acetaldehyde, formaldehyde, and acrolein) 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 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., S. Vance, P. Evansky, L. Copeland, R. Grindstaff, J. Dye, M. Higuchi, AND Ian Gilmour. Dose-Dependent Respiratory Impacts of Acrolein and TCE in Allergic Mice and Validation of In Vitro Effects. Society of Toxicology, NA (virtual meeting), Virtual, March 12 - 26, 2021.