Metabolic Perturbations Include Homocysteine Degradation and Polyamine Synthesis in Pathogenesis of Bronchopulmonary Dysplasia
Authors: Lee Daniel D. , Zacharias Lauren , Park Sang Jun , Zborek Kirsten , Sah Eric , Pajakowski Adam , Deberardinis Ralph , Schwarz Margaret A. 
Published: June 2021

IntroductionChanges in dynamic metabolic processes during lung development is not well known, particularly during the saccular and alveolar stages. Lungs of infants prematurely born during either stage have underdeveloped alveolar sacs with arrested growth and frequently require oxygen supplementation, which can result in lung disease of prematurity (bronchopulmonary dysplasia, BPD). Oxidation‐reduction (redox) processes are important in both lung development and pathogenesis; however, clinical studies attempting to limit BPD pathogenesis targeting redox processes have not been promising. In this study, metabolomics were utilized to identify alternative metabolic perturbations during the two lung development stages in an established murine model of hyperoxia‐induced BPD.MethodsPostnatal day (PN) 3 mice from pairs of pregnant dam mice were pooled, randomized, and left at normoxia (room air, 21% O2) or exposed to hyperoxia (85% O2) in a tight‐sealed, plexiglass chamber until PN 15. Nursing dams were rotated every 24 hours to limit oxygen toxicity. Lungs were isolated from mice on PN 1, 3, 5, 7, 10, and 15 within two minutes then snap frozen in liquid nitrogen. Following methanol extraction, metabolites were detected by liquid chromatography‐mass spectrometry. Statistics including partial least squares – discriminant analysis (PLS‐DA) and Variable Importance in Projection (VIP), i.e. a quantitative measure of discriminating metabolites, were performed using Python 2.7/3.0 and R.ResultsA series of analysis were performed to validate, identify, and characterize both significant metabolites and their involved pathways. Samples could be separated by both time and oxygen‐level using PLS‐DA. Enrichment analysis of metabolites with VIP ≥ 1 indicated that both the methionine‐homocysteine degradation cycle (p ≤ 1e‐4) and downstream of it, polyamine synthesis was perturbed (p ≤ 1e‐4). Components of both the arginine and glutathione metabolism pathways were also significantly enriched (p ≤ 1e‐4). Metabolites specifically found in the prior enrichment analysis (e.g., cystathione in glutathione metabolism, spermine, spermidine in polyamine synthesis) were significantly elevated in hyperoxic lung tissues on PN 5, 7, and 10 (one way ANOVA, p ≤ 1e‐2). Metabolites with a fold change of ≥ 1.3 from only day 5 lung tissues were significantly enriched for methylhistidine metabolism (p ≤ 1e‐5).ConclusionSignificant alterations of redox process such as glutathione or arginine metabolism were found which corroborate current studies in lung development and BPD. Yet other metabolic processes such as methionine‐homocysteine degradation and polyamine synthesis were discovered. Deregulation of the recycling of homocysteine into methionine and how it is further metabolized into polyamines is common in other pathogenesis. Further examination to intervene the deregulation in BPD pathogenesis may be attractive.Support or Funding InformationNIH Grant to MAS (R21 HD090227) and fellowship to DL (T32 HL091816‐09)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.