S-Nitrosoglutathione Reductase Inhibition Attenuates Long Term Effects of Neonatal Hyperoxia on Airway Hyperreactivity

Bronchopulmonary dysplasia survivors display long-term obstructive lung disease with airway hyperreactivity (AHR). While often treated with asthma medications, patient responses are variable. We have previously shown that the endogenous smooth muscle relaxant molecule, S-nitrosoglutathione (GSNO), is degraded in neonatal hyperoxia by upregulated GSNO reductase (GSNOR) in the murine lung (Raffay, et al. Molecular Pharmacology 2016; 90(4):418-26). We hypothesize that inhibition of GSNOR is a novel approach to attenuate neonatal hyperoxia-induced AHR in room air recovered mice. Newborn C57BL/6 mice were randomized on the first day of life and assigned to room air (21% O2) or hyperoxic (60% O2) groups for three weeks to induce bronchopulmonary dysplasia AHR. Animals were then recovered in room air until six weeks of age. AHR was assessed in vitro using precision-cut living lung slice preparations in response to increasing doses of bath-applied methacholine (MCh, 0.25–64 μM). Lung slices were pre-incubated with or without a GSNOR inhibitor (100 μM N6022) or a β2 adrenergic receptor agonist (10 or 100 μM levalbuterol). AHR is reported as percent change in airway lumen area from baseline (± SEM). 2–3 airways were imaged and averaged per animal per condition. Neonatal hyperoxia significantly increased airway contractile responses to MCh in room air recovered mice with a mean maximal effect (Emax) of 71.9 ± 2.7% change from baseline compared to the room air control Emax of 39.8 ± 5.2% (p<0.01). GSNOR inhibition significantly attenuated hyperoxic effects on AHR (32.2 ± 2.0%, p<0.001). Pre-incubation of hyperoxic slices with either a GSNOR inhibitor or a β2 adrenergic receptor agonist (100 μM) also attenuated the response to the maximal dose of MCh (64 μM) compared to vehicle (both p<0.01). These studies show that neonatal hyperoxia-exposed mice display longer-term in vitro AHR to MCh and that inhibition of GSNOR reverses hyperoxia-induced AHR comparable to a β2 adrenergic receptor agonist. We speculate that GSNO-based therapies may serve as novel treatments for AHR in bronchopulmonary dysplasia survivors that do not respond to β2 adrenergic receptor agonists. Support or Funding Information Supported by NIH 5K08HL133459-03 and ATS Research Foundation Unrestricted Critical Care Grant