Modeling Particulate Matter Exposure Using Mesh Nebulizers with Human Lung Cells

Particulate matter (PM) is a common air pollutant known to have negative health effects in humans. Investigating the effects and complexities of PM is important; however, concerns exist regarding the biological relevance of one of the most common exposure methods. In a cell culture model, liquid application involves the direct application of liquid condensates to the cell surface. This method has limitations, as it creates a hypoxic environment for cells and has been shown in previous research to cause unintended biological artifacts in airway cells. It is of interest to explore more biologically representative methods of PM exposure. We hypothesize that mesh nebulizers could be an effective alternative for modeling PM exposure in a human lung cell system. Mesh nebulizers turn liquid condensates into a fine aerosol and could potentially be used to deposit PM solutions onto cultured cells. To compare exposure methods, primary human bronchial epithelial cells (HBECs) were exposed to PM using both nebulization and liquid application. Endpoints for inflammation and hypoxia were then assessed to evaluate and compare the two methods. Hypoxia endpoints did not show that liquid application caused significantly higher levels of hypoxia markers compared to controls and nebulizer exposure. Evaluation of inflammatory markers revealed that neither method produced a significant inflammatory dose-response effect, and the data suggested that nebulizers do not induce as consistent an inflammatory response to PM exposure as liquid application. The results of this project do not support the original hypotheses; however, concerns still exist with liquid application, and we believe that mesh nebulizers may be a valuable tool for inhalation toxicology research. These findings suggest further investigation into the effects of liquid application on cultured airway cells, and into nebulizers as an alternative exposure method are needed.