Evaluation of an in vitro screening model to assess phosgene inhalation injury

Abstract

Therapeutic development against exposure to toxic gases is hindered by the lack of appropriate models to evaluate candidate compounds prior to animal efficacy studies. In this study, an in vitro, air-liquid interface exposure model has been tested to examine its potential application for screening treatments for phosgene (carbonyl chloride)-induced pulmonary injury. Epithelial cultures on Transwell^® inserts, combined with a Vitrocell^® exposure apparatus, provided a physiologically relevant exposure environment. Differentiated human bronchial epithelial (16HBE) cultures were exposed for 8 min to phosgene ranging from 0 to 64 ppm and assessed for changes in transepithelial electrical resistance (TEER, epithelial barrier integrity), cellular viability (XTT) and post-exposure (PE) cellular metabolic energy status. Exposure to phosgene concentrations ≥8 ppm caused dose-dependent and significant decreases in TEER and XTT which did not recover within 24-h PE. In addition, at 64 ppm the rate of oxidative glutamine metabolism was significantly inhibited at 6 and 24 h after exposure. Glycolytic activities (glucose utilization and lactate production) were also inhibited, but to a lesser extent. Decreased glycolytic function can translate to insufficient energy sources to counteract barrier function failure. Consistent and sensitive markers of phosgene exposure were TEER, cell viability and decreased metabolism. As such, we have assessed an appropriate in vitro model of phosgene inhalation that produced quantifiable alterations in markers of lung cell metabolism and injury in human airway epithelial cells. Data indicate the suitability of this model for testing classes of anti-edemagenic compounds such as corticosteroids or phosphodiesterase inhibitors for evaluating phosgene therapeutics.

Keywords:

• Phosgene
• transepithelial electrical resistance
• in vitro models
• energy metabolism
• pulmonary injury

Acknowledgments

The authors wish to thank Dr. Margaret Martens for her excellent assistance in performing the biochemical tests herein. We would also like to thank Dr. Dieter Gruenert of the California Pacific Medical Center Research Institute and the University of California, San Francisco for the gift of 16HBE cells cultures, as well as Mr. Justin Tressler, Mr. Chris Bowens and Ms. Ashley Rodriguez for their technical assistance on this project. Excellent graphics assistance was provided by Mr. James Abraham.

Disclosure statement

The authors declare that there are no conflicts of interest.

Funding

This project was supported by an Interagency Agreement between NIH/NIAID and the USAMRICD (Y1-A1-6179-02 "Chemicals Affecting the Respiratory Tract – Pulmonary Toxicant Gases"). The opinions and conclusions in this study are solely those of the authors and are not those of the NIH.