Hemoxygenase-1 as a key mediator of acute radiation pneumonitis revealed in a human lung alveolus-on-a-chip

Exposure to gamma radiation either due to environmental disasters or cancer radiotherapy can result in development of acute radiation syndrome (ARS), characterized by pneumonitis and lung fibrosis. We leveraged a microfluidic organ-on-a-chip lined by human lung alveolar epithelium interfaced with pulmonary endothelium to model acute radiation-induced lung injury in vitro. Both lung epithelium and endothelium exhibited DNA damage, cellular hypertrophy, upregulation of inflammatory cytokines, and loss of barrier function within 6 h of radiation exposure, although greater damage was observed in the endothelium. Transcriptomic analysis revealed increased expression of the cytoprotective gene, hemoxygenase-1 (HMOX-1) and gene network analysis identified it as a central mediator of radiation-induced injury. Pharmacological stimulation of HMOX-1 activity also significantly reduced acute radiation-induced lung injury, although it enhanced damage at later times. Thus, this human lung chip offers a new platform to study ARS and these results suggest that HMOX-1 may be mechanistically involved in this injury response.