Hyperoxia-activated circulating extracellular vesicles

This study is about Hyperoxia-induced lung injury plays a key role in the development of bronchopulmonary dysplasia (BPD), characterized by inflammatory injury and impaired lung development in preterm infants. Although BPD is a predictor of poor neurodevelopmental outcomes, currently it is uncertain how lung injury contributes to brain injury in preterm infants. Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that regulate intercellular and inter-organ communications. Gasdermin D (GSDMD) has emerged as a key executor of inflammasome-mediated cell death and inflammation. In this study, we utilized a neonatal rat model of BPD to assess if hyperoxia stimulates lung release of circulating EVs and if these EVs induce lung and brain injury. We found that hyperoxia-exposed rats had elevated numbers of plasma-derived EVs compared to rats maintained in room air. These EVs also had increased cargos of surfactant protein C, a marker of type II alveolar epithelial cells (AEC), and the active (p30) form of GSDMD. When these EVs were adoptively transferred into normal newborn rats via intravenous injection, they were taken up both by lung and brain tissues. Moreover, EVs from hyperoxic animals induced not only the pathological hallmarks of BPD, but also brain inflammatory injury in recipient rats, as well as inducing cell death in cultured pulmonary vascular endothelial cells and neural stem cells (NSC).

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Fig: Hyperoxia stimulates the release of EVs with an increased cargo of SPC/GSDMD into the circulation of neonatal rats. Newborn rats on postnatal day 1 (P1) were exposed to room air (RA) or hyperoxia, 95% O2 (O2) for 14 days and EVs were isolated from the plasmas of these animals. Nanosight tracking assay showed that both room air-exposed EVs (RA-EVs, (A)) and hyperoxia-exposed EVs (O2-EVs, (B)) contained particles that were prodominately 100–150 nm in diameter, but O2-EVs had increased particle concentrations as compared to RA-EVs ((C), n = 6/group, *P < 0.05). FACS analysis demonstrated that RA-EVs (D) had a smaller population of SPC + /GSDMD + EVs compared to O2-EVs (E) ((F), n = 4/group, *P < 0.05). (G) Representative Western blots of SPC, GSDMD, CD9 and CD63. O2-EVs had increased cargos of SPC (H) and GSDMD-p30 (I) compared to RA-EVs (n = 6/group, **P < 0.01).

Similarly, hyperoxia-exposed cultured AEC-like cells released EVs that also contained increased GSDMD-p30 and these EVs induced pyroptotic cell death in NSC. Overall, these data indicate that hyperoxia-activated circulating EVs mediate a lung to brain crosstalk resulting in brain injury and suggest a mechanism that links lung injury and neurodevelopmental impairment in BPD infants.

Ali, A., Zambrano, R., Duncan, M.R. et al. Hyperoxia-activated circulating extracellular vesicles induce lung and brain injury in neonatal rats. Sci Rep 11, 8791 (2021). https://doi.org/10.1038/s41598-021-87706-w

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