Role of ROS, soluble guanylate cyclase and cGMP in mouse lung development during hyperoxia

Bronchopulmonary dysplasia (BPD) is characterized by disruption of newborn lung alveolar and vascular development. Administration of supplemental O₂ predisposes to BPD by inducing oxidant stress in multiple subcellular compartments by augmenting reactive oxygen species (ROS) production. We studied the role of subcellular ROS in lung cyclic guanosine monophosphate (cGMP) signaling and its relationship to lung development in cells, embryonic lung explants, and newborn mice. Embryonic lung explants demonstrated increased mitochondrial ROS during hyperoxia. In hyperoxic human embryonic kidney 293T cells, ROS in the mitochondrial matrix, cytosol, and intermembrane space (IMS) increased. Those cells demonstrated impaired soluble guanylate cyclase (sGC)-cGMP responsiveness to a nitric oxide donor, a response prevented by the cytosolic glutathione mimetic ebselen as well as by the sGC activator, cinaciguat, but not by mitochondrial matrix-targeted ebselen or by expression of an H₂O₂ scavenger in the mitochondrial intermembrane space (IMS-Prdx5). Neonatal mice exposed to 75% O₂ for 2 wk exhibited alveolar simplification and pulmonary artery wall thickening that were not rescued by cinaciguat or the sGC stimulator, riociguat. However, previous work demonstrated that mitochondria-targeted antioxidants prevent hyperoxia-mediated inhibition of lung alveolar development. Collectively, these studies demonstrate that separate mechanisms underlie the effects of hyperoxia on cGMP signaling and alveolarization in the newborn lung, with cytosolic oxidant stress responsible for impairing cGMP signaling and mitochondrial matrix ROS mediating the hyperoxia-induced impairment in lung alveolar development. Hence, the impairments in cGMP signaling and lung alveolar development during hyperoxia involve oxidant stress in distinct subcellular compartments and occur through independent mechanisms.NEW & NOTEWORTHY Hyperoxia impairs NO-mediated cGMP generation by augmenting cytosolic ROS. Cinaciguat rescued cGMP responsiveness in hyperoxic cells, hence oxidative damage to sGC is responsible. Increases in ROS in hyperoxic embryonic mouse lungs recapitulated responses previously recorded in adult mice. Hence, unlike premature infants, late gestational lung antioxidant maturation in the mouse is robust. Defects in lung alveolarization induced by hyperoxia were not rescued by cinaciguat or riociguat; hence, impaired cGMP signaling does not impair lung alveolarization.