Flavin adenine dinucleotide (FADH) protects the preterm lung from hyperoxic injury
Authors: Montgomery Hunter , Li Chao Ying , Zimmerman Elizabeth , Paine Robert , Helms My N. 
Published: May 2023

Background: Bronchopulmonary dysplasia (BPD) is a severe oxidative-stress induced lung disease that primarily affects premature infants requiring long term oxygen supplementation. BPD is characterized by attenuated lung development, fibrosis, inflammation, and airway smooth muscle hyperplasia. Our research objective was to test a novel hypothesis that evaluates whether providing flavin adenine dinucleotide (FADH) can reduce oxidative stress and prevent high oxygen induced lung injury using a mouse model for BPD. FADH is a cofactor for glutathione reductase (GR) enzymatic activity, responsible for recycling the bioavailability of the antioxidant glutathione (GSH) under oxidizing conditions. Methods: We used a hyperoxia-induced lung injury term mouse model (0.85 fraction inspired oxygen; FiO2) to recapitulate the BPD phenotype for experimental study. Briefly, newborn mice were housed in 0.85 FiO2 (hyperoxic) or 21% O2 (normoxic) conditions from birth until post-natal day (PN) 14. Following O2 exposures, FADH (7 μM) or vehicle (saline) treatments were insufflated daily on PN 14-21 (1.5μL/g body weight). Bronchoalveolar lavage fluid (BALF) and lung tissue samples were collected and evaluated for redox stress, lung injury/alveolar development, and inflammation using commercially available GSH Assay kits (Abcam), standard immunohistochemistry, and LEGENDplex inflammation panels (Biolegend), respectively. Male and female mice were randomly assigned to study groups. Single data comparisons were performed using paired Student’s t-tests. Multiple comparisons were performed using one-way analysis of variance followed by post-hoc testing in Sigma Plot (SPSS Inc). Results: Daily insufflation of FADH improved neonatal lung health following chronic 0.85 FiO2 exposure, as indicated by measured BALF GSH/GSSG redox potentials (Eh). Eh=-179.10 mV ± 1.85 mV in the FADH treated groups (n=5), wherein vehicle treated lungs were more oxidatively stressed with BALF Eh=-168.77 mV ± 3.64 mV (n=3 independent litters; P=.02). Morphometric analysis of lung development and lung injury scores were significantly improved in 0.85 FiO2 exposed pups receiving FADH treatment vs. vehicle control pups ( P<.001; n=3 litters). FADH treatments also suppressed neutrophil infiltration (n=10; P<.001) with significant increase in IL-12p70 ( P<.05) and TNF-α ( P<.05; n=3 litters) in hyperoxic lungs. Conclusions: FADH protects the preterm lung from hyperoxic injury, albeit the mechanisms remain unclear. Importantly, we show that FADH increases the bioavailability of the antioxidant GSH, as well as IL12-p70 and TNF-α. The signaling molecules identified have known anti- and pro-inflammatory effects in the lungs and will therefore be explored in future studies as potential therapeutic targets involved in the pathogenesis of high-oxygen induced lung injury. Supported by T35DK103596 (HM) and R01HL137033 (MH). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.