Oxygen-induced airway hyperreactivity is mediated through expression of S-nitrosoglutathione reductase in the lung epithelium of neonatal mice

Background: Premature infants exposed to supplemental oxygen are at increased risk for airway hyperreactivity (AHR) and other wheezing disorders. S-nitrosoglutathione (GSNO) is an endogenous smooth muscle relaxant degraded by GSNO reductase (GSNOR). Elevated GSNOR has been implicated in the development of asthma and bronchopulmonary dysplasia (BPD), a chronic lung disease of prematurity. GSNOR-/- mice are protected from AHR in both asthma and BPD models. Selective deletion of GSNOR in the smooth muscle did not protect against oxygen-induced AHR in the BPD model. We speculate that this was because GSNOR remained highly expressed in the lung epithelium. Therefore, we hypothesize that selective epithelial deletion of GSNOR using a Cre-Lox recombination system will prevent oxygen-induced AHR in neonatal mice. Methods: Newborn wildtype C57BL/6 and Cre-loxP epithelium knockout mice (SFCGflox) were similarly treated with tamoxifen for 5 postnatal days (P0-4), by injecting the lactating dams (100 μL/day; 20 mg/mL i.p) to induce cell-specific GSNOR deletion in bronchiole epithelium Club cells and Type-2 alveolar epithelial cells. Litters were then raised in room air or 60% oxygen (hyperoxia) (P7-21). Methacholine (MCh, 0.25-64 μM )-induced airway constriction was measured in vitro using precision-cut living lung slice preparations. The results are expressed as mean values of percentage of the initial area of the airway lumen. 2-3 airways were imaged and averaged per animal per condition. In P21 littermates, mean linear intercepts (MLI) were quantified in inflation-fixed H&E-stained lung sections. Results: In hyperoxia-exposed wildtype mice, MCh-induced intrapulmonary airway contractile responses were significantly higher with a mean maximal effect (Emax) 64.34% change from baseline compared to room air controls (Emax 45.88%) (p< 0.001). In SFCGflox mice exposed to hyperoxia, MCh-induced airway contractile responses were significantly lower compared to hyperoxia-exposed wildtype mice with a mean Emax 49.14% (p< 0.001). The contractile responses between hyperoxia- and room air-exposed SFCGflox mice did not differ significantly. There was a trend of increase in MLI in hyperoxia-exposed wild-type mice, however the difference is not significant compared to room air-exposed wild-type mice. Conclusion: Neonatal oxygen exposure increased airway reactivity in this mouse model. These data suggest that selective genetic deletion of GSNOR from the lung epithelium was protective against the adverse effects of oxygen on AHR. GSNOR inhibitors being developed to treat other pulmonary diseases may provide benefits in premature patients at risk for reactive airway disease. Funding: NIH R01HL172894 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.