Alterations in VASP phosphorylation and profilin1 and cofilin1 expression in hyperoxic lung injury and BPD.

BACKGROUND: Hyperoxia is a frequently employed therapy for prematurely born infants, induces lung injury and contributes to development of bronchopulmonary dysplasia (BPD). BPD is characterized by decreased cellular proliferation, cellular migration, and failure of injury repair systems. Actin binding proteins (ABPs) such as VASP, cofilin1, and profilin1 regulate cell proliferation and migration via modulation of actin dynamics. Lung mesenchymal stem cells (L-MSCs) initiate repair processes by proliferating, migrating, and localizing to sites of injury. These processes have not been extensively explored in hyperoxia induced lung injury and repair. METHODS: ABPs and CD146(+) L-MSCs were analyzed by immunofluorescence in human lung autopsy tissues from infants with and without BPD and by western blot in lung tissue homogenates obtained from our murine model of newborn hyperoxic lung injury. RESULTS: Decreased F-actin content, ratio of VASP(pS157/VASPpS239), and profilin 1 expression were observed in human lung tissues but this same pattern was not observed in lungs from hyperoxia-exposed newborn mice. Increases in cofilin1 expression were observed in both human and mouse tissues at 7d indicating a dysregulation in actin dynamics which may be related to altered growth. CD146 levels were elevated in human and newborn mice tissues (7d). CONCLUSION: Altered phosphorylation of VASP and expression of profilin 1 and cofilin 1 in human tissues indicate that the pathophysiology of BPD involves dysregulation of actin binding proteins. Lack of similar changes in a mouse model of hyperoxia exposure imply that disruption in actin binding protein expression may be linked to interventions or morbidities other than hyperoxia alone.