FoxO factors are essential for maintaining organ homeostasis by acting as stress sensors in airway epithelial cells

Abstract

Airway epithelia must maintain functional and structural homeostasis despite exposure to diverse environmental stressors. FoxO transcription factors are well suited to this task, acting as integration hubs that translate extrinsic and intrinsic signals into appropriate physiological responses. We show that FoxO factors in Drosophila, mouse, and human airway epithelial cells (AECs) undergo nuclear translocation in response to stressors including hypoxia, temperature, and oxidative stress. In human airway epithelial cell lines, individual hFOXO factors show distinct, cell-type-specific activation patterns. In Drosophila, hypoxia was the only stressor among those tested that triggered a dfoxo-dependent innate immune response. Because Drosophila possesses a single FoxO ortholog, loss-of-function analysis directly demonstrated that dfoxo is required for stress resistance in the airway epithelium. Reduced FoxO expression was similarly observed in mouse models of asthma and in airway samples from asthma patients, paralleling the increased stress sensitivity seen upon FoxO loss in flies. While our data do not establish that reduced FOXO levels cause asthma, they indicate that FoxO-dependent stress pathways are altered in diseased airways across species. Together, these findings support a model in which FoxO coordinates adaptive epithelial stress responses that maintain airway homeostasis under environmental challenge.