Abstract 4142283: Opposing Responses to Oxygen in the Rabbit Ductus Arteriosus and Fetal Pulmonary Arteries: Proteomic Analysis Reveals Significant Metabolic Differences

Introduction: The ductus arteriosus (DA) is a fetal vessel connecting the pulmonary artery (PA) and aorta, diverting oxygenated blood away from the developing lungs to the systemic circulation. Following the first breath, the DA rapidly constricts in response to increased arterial oxygen (O 2 ) which simultaneously induces relaxation of small resistance pulmonary arteries (rPA). These changes, vital for adaptation to neonatal life, separate the pulmonary and systemic circulations (DA vasoconstriction) and enable adequate perfusion of newly ventilated lungs (PA vasodilation). The underlying mechanism of these opposite O 2 responses is not fully understood. A failure of either vessel to appropriately respond to O 2 results in clinical complications, notably persistent ductus arteriosus or persistent pulmonary hypertension of the newborn. To examine the underlying differences in these fetal vessels, we performed proteomics on fetal rabbit DA and rPA. Methods: DA and rPA were isolated from male (n=4) and female (n=4) term (30 days gestation) fetal New Zealand white rabbits (protocol #2021-2122). Extracted protein was labelled with TMTpro mass tag labeling. Following HPLC fractionation, samples were run on the ThermoFisher Orbitrap Eclipse Mass Spectrometer. Analysis was completed using ThermoFisher Proteome Discoverer software and DESeq2. Results: There were 3103 significantly, differentially expressed proteins between the DA and PA(Benjamini Hochberg adjusted p<0.05), 232 of which were ±1.5-fold differentially expressed ( Figure 1 ). Using KEGG pathway analysis the most significantly DA enriched pathway is “Starch and sucrose metabolism” (map00500) and the most significantly rPA enriched pathway is “Sulfur Metabolism” (map00920). There was also rPA enrichment of other metabolic pathways including “Fatty Acid Degradation” (map00071), “Pyruvate Metabolism” (map00620), and “Glycolysis/Gluconeogenesis” (map00010). Conclusions: This analysis reveals unique mitochondrial metabolic pathways that may contribute to the opposing tissue responses of these specialized blood vessels to O 2 . Exploration of these pathways may identify potential therapeutic targets and inform future investigations of differential O 2 sensing in DA and rPA.