An in vitro, architecturally relevant, alveolar model to assess potential for respiratory sensitization.

With greater numbers of the global population entering urban areas and subsequently noting increases in respiratory illness and disease, it is of utmost importance to understand the mechanisms and potential for inhaled air (containing both chemical and particulate) to lead to adverse human health effects. Novel substances, specifically chemicals and particulates, are well-documented for their ability to cause respiratory allergies and sensitizing reactions. Many of these materials are produced to advance industry, consumer, and medicinal products. The standard for toxicological testing involves the use of a single cell type relevant to the potentially exposed organ, e.g., epithelial cells for dermal testing. However, in any biological system multiple cell-types exist where inter and intracellular communication, cell turn-over, clearance mechanisms, and a variety of movements are involved. The goal of this dissertation was to develop and utilize an architecturally relevant respiratory model to assess and study the potential biological impact of both known respiratory sensitizers and unknown materials to gain important insights into the early steps involved in forming a sensitizing reaction in the lungs. While it is possible for sensitization to occur within any compartment within the lungs, a simplistic, reliable, reproducible model where endpoint measurements can be modified has yet to be established. In this study, an in vitro alveolar model designed to mimic in vivo architecture was utilized to characterize cell types and analyze responses at the cellular, biochemical, and gene expression levels after exposure to known respiratory sensitizers, known non-respiratory sensitizers, and unknown materials. First, a chemical respiratory sensitizer was compared to a general cell activator to determine differences between overall cell activation and specifics of sensitization. Next, a respiratory irritating particulate and a suspected respiratory sensitizing particulate were used to understand differences between irritation and sensitization. Finally, an in-depth gene expression analysis was performed on two known respiratory sensitizers and compared to two known non-respiratory sensitizers to gain insight of the total gene expression analyses that occurs after chemical respiratory sensitizers are inhaled. Ultimately, the aim of this work is to advance the knowledge base of respiratory immunotoxicology by improving the understanding of what cellular perturbations may occur after inhalation to potential sensitizing substances; aid in the preventing risky materials from entering production and the environment; aid in risk assessment and regulations; and understand how adverse health outcomes can be prevented or treated.