Peptidome Analysis Of Lung Tissues From Hyperoxia-induced Bronchopulmonary Dysplasia Mouse Model: Insights Into The Pathophysiological Process Of Bronchopulmonary Dysplasia

Objective:Bronchopulmonary dysplasia(BPD),a neonatal form of chronic lung disease,could lead to increased risk of pulmonary and brain impairment persisting into adulthood.BPD has also been associated with a high mortality rate especially in the extremely preterm infants.This so called “new” BPD results from mechanical ventilation,hyperoxia and infection on the immature lung,reflecting disturbed development of the alveoli and the pulmonary vasculature and pulmonary hypertension.The characteristic pathologic features of diseased lung include inhibition of microvascular development,extensive extracellular matrix(ECM)remodeling,alveolar simplification,mild interstitial thickening and inflammation.Many interventions have been tested to reduce the risk of BPD in clinical trials.However,only a few have demonstrated significant therapeutic effects.Therefore,earlier disease prediction is warranted to initiate preventive strategies in patients.The aim of this study was to identify and compare the peptidomic profiles of lung tissues from neonatal mice with and without bronchopulmonary dysplasia(BPD).Methods:Hyperoxia was used as a tool to establish the BPD mouse model.Lung tissues were obtained on postnatal day 9(PND 9).Samples were analyzed by histological sections and label-free liquid chromatography-mass spectrometry(LC-MS/MS)approach.The general characteristics of the peptides,such as amino acid numbers,molecular weight(MW),and isoelectric point(p I)were analyzed.Gene ontology(GO)and pathway enrichment analysis were performed to explore the potential functions of the differentially expressed peptides and their precursor protein.The protein-protein interaction of differentially expressed peptides and their protein precursors was analyzed by Uni Prot database and STRING.The conservation of amino acid sequences across species was determined by the basic local alignment search tool(BLAST).Results:Histological analysis of lung sections showed significant alveolar simplification and aberrant pulmonary vascularization in BPD group.We totally identified 3704 peptides,of which 63 peptides were differentially expressed in the lung tissues of BPD group compared with control.Among them,31 peptides were down-regulated and 32 peptides were up-regulated.Most peptides were less than 24 amino acids in length,ranging from 1,000-3,500 Da in MWand 3.0-7.0 in Pi.In down-regulated group,the four primary amino acids of cleavage site were Lysine(L),Lysine/Serine(L/S),Lysine(L),and Phenylalanine(F),while in up-regulated group,the four primary amino acids of cleavage site were Lysine(L),Alanine/Lysine/Serine(A/L/S),Lysine(L),and Phenylalanine/Valine(F/V).Bioinformatics analysis suggested several potential roles of differentially expressed peptides in the pathophysiological process of BPD.We found that the down-regulated peptide derived from the functional domain of polypyrimidine tract-binding protein 1(PTBP1)and the up-regulated peptide derived from the functional domain of electron transfer flavoprotein subunit alpha(ETFA)might be associated with the pathophysiological process of BPD.Conclusion:In our hyperoxia induced BPD mouse model,histological analysis of lung sections showed significant alveolar simplification and aberrant pulmonary vascularization,the typical histopathological features of BPD in clinic.The peptide contents in the lung tissue from both the CTL and BPD mouse were significantly different.Bioinformatics analysis suggested several potential roles of differentially expressed peptides in the pathophysiological process of BPD.This study highlights novel peptide candidates and provides new insights for further understanding of the molecular mechanism of BPD development.