571 - Furin regulates the alveolarization of neonatal lungs in a mouse model of hyperoxic lung injury

Poster Number: 571
Publication Number: 571.1448

Background: Bronchopulmonary dysplasia (BPD) remains an important prognostic factor in preterm infants. Current therapeutic options, such as corticosteroid administration and less invasive respiratory support, have not achieved a convincing improvement in outcomes. We previously reported that furin, one of the major proprotein convertases, regulates changes in smooth muscle cell phenotypes by modulating the proteolysis of cyclic guanosine monophosphate-dependent protein kinase I, suggesting its critical role in BPD pathogenesis.

Objective: We aimed to evaluate whether furin regulates the alveolarization of immature lungs by activating alveolarization-driving proteins.

Design/Methods: Within 12 hours after birth, C57BL6J mice pups and their mothers were randomly exposed to either air or 85% O2 for 10 days. Furin and its target IGF-IR immunoreactivity were determined using the immunohistochemistry of fixed lung slices, or whole lung lysate of snap-frozen lungs at P 10. Alveolar maldevelopment was determined based on mean linear intercept and tissue volume density using light microscopy. For immunocytochemistry and protein detection, primary myofibroblast cell cultures were prepared from P1 mice pups. We first examined the expression levels and functions of furin using the hyperoxia-induced BPD mouse model. Subsequently, we treated normoxic mice pups and primary myofibroblast cell cultures with furin inhibitors. Finally, we administered the hyperoxia-exposed mice pups with recombinant furin.

Results: Furin-positive cells were observed at the tips of the secondary alveolar septa, and immunofluorescence revealed the co-expression of furin with alpha-smooth muscle actin (Fig 1). Hyperoxia exposure for 10 days decreased alveolar formation and the expression of furin and its target IGF-1R. Hexa-D-arginine administration also significantly inhibited alveolar formation. Another furin inhibitor, decanoyl-RVKR-chloromethylketone, increased the accumulation of the pro-IGF-1R fraction and decreased IGF-1R phosphorylation in the immunoblotting using myofibroblast primary cultures (Fig 2). Finally, recombinant furin treatment significantly improved alveolarization in hyperoxia-exposed mice pups (Fig 3).

Conclusion(s): These findings suggest that furin regulates alveolarization in immature lungs. Therefore, this study provides novel insights regarding the involvement of furin in BPD pathogenesis and highlights a potential treatment target for ameliorating the impact of BPD.