Interaction with Epithelial Cells Modifies Airway Macrophage Response to Ozone

The initial innate immune response to ozone (O-3) in the lung is orchestrated by structural cells, such as epithelial cells, and resident immune cells, such as airway macrophages (Macs). We developed an epithelial cell-Mac coculture model to investigate how epithelial cell-derived signals affect Mac response to O-3. Macs from the bronchoalveolar lavage (BAL) of healthy volunteers were cocultured with the human bronchial epithelial (16HBE) or alveolar (A549) epithelial cell lines. Cocultures, Mac monocultures, and epithelial cell monocultures were exposed to O-3 or air, and Mac immunophenotype, phagocytosis, and cytotoxicity were assessed. Quantities of hyaluronic acid (HA) and IL-8 were compared across cultures and in BAL fluid from healthy volunteers exposed to O-3 or air for in vivo confirmation. We show that Macs in coculture had increased markers of alternative activation, enhanced cytotoxicity, and reduced phagocytosis compared with Macs in monoculture that differed based on coculture with A549 or 16HBE. Production of HA by epithelial cell monocultures was not affected by O-3, but quantities of HA in the in vitro coculture and BAL fluid from volunteers exposed in vivo were increased with O-3 exposure, indicating that O-3 exposure impairs Mac regulation of HA. Together, we show epithelial cell-Mac coculture models that have many similarities to the in vivo responses to O-3, and demonstrate that epithelial cell-derived signals are important determinants of Mac immunophenotype and response to O-3.