175 - Mice Lacking the NAD(P)H quinone oxidoreductase (NQO1 or NQO2) Genes are More Susceptible than Wild Type Mice to Hyperoxic Lung Injury in vivo: Protection by β-napthoflavone (BNF) Treatment

Saturday, April 29, 2023

3:30 PM – 6:00 PM ET

Poster Number: 175
Publication Number: 175.218

Sandra L. Grimm, Baylor College of Medicine, Houston, TX, United States; Weiwu Jiang, Baylor College of Medicine, Pearland, TX, United States; Rachel Stading, Baylor College of Medicine, Houston, TX, United States; Cristian Coarfa, Baylor College of Medicine, Houston, TX, United States; Bhagavatula Moorthy, Baylor College of Medicine, Houston, TX, United States

Presenting Author(s)

SG

Sandra L. Grimm, PhD (she/her/hers)

Instructor
Baylor College of Medicine
Houston, Texas, United States

Background: Supplemental oxygen administration (hyperoxia) for pulmonary insufficiency contributes to bronchopulmonary dysplasia (BPD) in premature infants and ALI/ARDS in children and adults. NAD(P)H quinone reductase (NQO1) and dehydrogenase (NQO2) are xenobiotic metabolizing enzymes that play a role in redox processes upon hyperoxia exposure.

Objective: We tested the hypothesis that mice lacking the gene for Nqo1 or Nqo2 will be more susceptible to hyperoxic lung injury in vivo, compared to wild type (WT) mice, and that pretreatment of these mice with the cytochrome P4501A inducer ß-napthoflavone (BNF) will rescue this phenotype.

Design/Methods: At 10–12 weeks of age WT C57BL/6J, Nqo1-null, or Nqo2-null mice were treated i.p. with vehicle (corn oil) or BNF (40 mg/kg), once daily for 4 days. The animals were then maintained in room air or exposed to hyperoxia for 24–72h. Lungs (4 mice/group) were frozen for RNA isolation and subsequent RNA-Sequencing. Lung injury was assessed by histology and neutrophil recruitment. All data were analyzed using 2-way ANOVA with p< 0.05 considered statistically significant.

Results: Compared to WT mice, the Nqo1- and Nqo2-null mice were more susceptible to oxygen-mediated lung damage and inflammation, as evidenced by increased lung:body weight ratios, lung injury, neutrophil recruitment, and augmented expression of IL-6 and TNF-α. There was no significant difference in the extent of lung injury between null mice. BNF treatment led to attenuation of lung injury and increased expression of Cyp1a1 in all 3 genotypes. Differentially expressed genes (DEGs) were identified by RNA-Seq. Many DEGs dysregulated upon hyperoxia exposure were reversed upon BNF treatment, and from those genes we selected those that were more severely dysregulated upon loss of Nqo1 or Nqo2 compared to WT. Genes commonly regulated by Nqo1 and Nqo2 after hyperoxia included Il-6, Cxcl2, Apold1, Fosb, and others (29 total). An additional 46 and 52 genes were regulated by specifically by Nqo1 or Nqo2, respectively. Pathway analysis using the 29 common DEGs enriched for Hallmark pathways of TNF-α signaling, Inflammatory response, and Hypoxia.

Conclusion(s):

Our observation that BNF-pretreated mice showed attenuation of hyperoxic lung injury and augmented pulmonary CYP1A1 expression supports the hypothesis that BNF is protective via induction of CYP1A enzymes. Future research will examine gene and pathway alterations in Nqo1- and Nqo2-null mice to delineate the protective role NQO enzymes play in lung injury, which could lead to the development of novel strategies for prevention and/or treatment of BPD and ALI/ARDS.