Introduction Neonatal lung injury as a consequence of hyperoxia (HO) therapy and ventilator care contribute to the development of bronchopulmonary dysplasia (BPD). Increased expression and activity of lysyl oxidase (LOX), a key enzyme that cross-links collagen, was associated with increased sphingosine kinase 1 (SPHK1) in human BPD. We, therefore, examined closely the link between LOX and SPHK1 in BPD.
Method The enzyme expression of SPHK1 and LOX were assessed in lung tissues of human BPD using immunohistochemistry and quantified (Halo). In vivo studies were based on Sphk1−/− and matched wild type (WT) neonatal mice exposed to HO while treated with PF543, an inhibitor of SPHK1. In vitro mechanistic studies used human lung microvascular endothelial cells (HLMVECs).
Results Both SPHK1 and LOX expressions were increased in lungs of patients with BPD. Tracheal aspirates from patients with BPD had increased LOX, correlating with sphingosine-1-phosphate (S1P) levels. HO-induced increase of LOX in lungs were attenuated in both Sphk1−/− and PF543-treated WT mice, accompanied by reduced collagen staining (sirius red). PF543 reduced LOX activity in both bronchoalveolar lavage fluid and supernatant of HLMVECs following HO. In silico analysis revealed STAT3 as a potential transcriptional regulator of LOX. In HLMVECs, following HO, ChIP assay confirmed increased STAT3 binding to LOX promoter. SPHK1 inhibition reduced phosphorylation of STAT3. Antibody to S1P and siRNA against SPNS2, S1P receptor 1 (S1P1) and STAT3 reduced LOX expression.
Conclusion HO-induced SPHK1/S1P signalling axis plays a critical role in transcriptional regulation of LOX expression via SPNS2, S1P1 and STAT3 in lung endothelium.
- paediatric lung disaese
- long term oxygen therapy (LTOT)
- oxidative stress
- paediatric interstitial lung disease
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information. All data are available and presented with the manuscript.
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AWH and TB contributed equally.
Contributors AWH and TB participated in the study design, performed experiments, interpreted results, prepared figures and edited the manuscript. DLE contributed to conceptualising the study, performed experiments, interpreted results and prepared figures. TSe performed experiments, interpreted results, prepared figures and analysed data. TSu performed experiments, interpreted results, prepared figures, analysed the data and edited the manuscript. LAM performed experiments, interpreted results, prepared figures and analysed the data. SG assisted the design of the study, interpreted results and edited the manuscript. GSP guided the conceptualisation and design of the study, interpreted results and edited the manuscript. VN conceptualised the study and its design, interpreted results and edited the manuscript. AH conceptualised the study and its design, performed experiments, analysed data, interpreted results, drafted and edited the manuscript. All the authors read and approved the final manuscript.
Funding This work was supported in part by R01HD090887-01A1 from NICHD to AH. The BRINDL repository is funded by NHLBI U01HL122700 and U01HL148861. No role was played by the funding body in the design of the study, collection, analysis and interpretation of data or in writing the manuscript.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.