View Abstract

A2824 - The Small Molecule Antipsychotic Aripiprazole Potentiates Ozone-Induced Inflammation in Airway Epithelium
Author Block: J. Hoffman1, A. M. Speen2, H. Kim3, M. E. Rebuli2, N. A. Porter3, I. Jaspers2; 1Curriculum for the Environment and Ecology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 3Department of Chemistry and Center for Molecular Toxicology, Vanderbilt University, Nashville, TN, United States.
Rationale
More than a third of the U.S. population lives in areas exceeding the 2015 National Ambient Air Quality Standard for ozone (O3). While conditions, such as pre-existing respiratory disease, have been identified as factors enhancing susceptibility to O3-induced health effects, the potential for drug x environment interactions in further sensitizing populations has not yet been studied. We have previously demonstrated that in the airways, O3-induced oxidation of cholesterol forms reactive and electrophilic oxysterols capable of adducting proteins and perturbing normal cellular signaling. In this regard, the consequences of drugs which modify cholesterol synthesis needs to be understood. Widely prescribed small molecule antipsychotics like aripiprazole/Abilify™ (APZ) reduce the activity of 7-dehydrocholesterol reductase (DHCR7) activity, thus altering normal cholesterol synthesis and increasing 7DHC, which is significantly more susceptible to O3-induced oxidation than cholesterol.
Methods
Human bronchial airway epithelial cells (ECs), 16HBEs, were grown at air-liquid-interface and treated with varying concentrations of APZ. Cells were subsequently exposed to 0.4 ppm O3 for 4 hours and analyzed for markers of inflammation 1 hour post-exposure. LC-MS/MS analysis quantified 7DHC and cholesterol levels in whole cell lysates. Levels of IL-8 and IL-6 mRNA and protein, as well as inflammation/immune gene expression profiles were assessed. To determine whether effects of APZ on inflammation are O3 specific, cells were stimulated with TNFα after APZ treatment. Direct effects of O3 on cholesterol and 7DHC were compared by treating ECs with ozonized buffer containing cholesterol or 7DHC and examining IL-8 expression 1 hour post-exposure.
Results
Our results show that APZ administered at clinically relevant concentrations increased 7DHC levels in ECs. Treatment with APZ followed by exposure to O3 caused an increased inflammatory response in ECs, marked by enhanced gene expression of pro-inflammatory cytokines IL-6 and IL-8 as compared to the O3-exposed vehicle control. In contrast, when APZ treatment was followed by exposure to various concentrations of TNFα, cells exhibited no APZ-induced increase in IL-6 and IL-8 expression. Furthermore, cells supplemented with ozonized 7DHC showed a greater increase in IL-8 expression as compared to the vehicle control or ozonized cholesterol alone.
Conclusions
Evidence provided here indicates that APZ potentiates O3-induced inflammation in ECs. Our data suggest that modification of cholesterol synthesis provides a mechanistic basis for a novel drug x environment interaction between APZ and O3. Considering the prevalent use of APZ and widespread exposure to O3, these data have significant public health implications.