Bronchopulmonary dysplasia (BPD) is a chronic lung disease that affects prematurely born infants and appears to evolve in part from early inflammatory responses in the lung. The inflammatory responses have been associated with protein and lipid oxidation in tracheal aspirate fluids. The present study was designed to test the hypothesis that in the first week of life specific oxidations and/ or altered expressions of proteins would be observed in tracheal aspirate fluids in infants who would subsequently develop BPD. We obtained tracheal aspirate fluids on Days of life 1, 3, and 6 from infants born at < or = 29 wk gestation, incubated the fluids with 2,4-dinitrophenylhyrazine (DNPH), separated the proteins electrophoretically, and assessed DNPH reactivity by immunonblots. DNPH reactivity of a protein that was identified as Clara cell secretory protein (CCSP) was observed more consistently in tracheal aspirate fluids from infants who later developed BPD than from infants who did not develop BPD. Tracheal aspirate fluid levels of immunoreactive CCSP were also lower on Day of life 1 in infants who developed BPD than in those who did not develop BPD. Increased CCSP oxidation and decreased immunoreactive CCSP expression in infants who subsequently developed BPD suggest that Clara cell function and CCSP expression may be critical for normal bronchoalveolar fluid homeostasis and that maintaining CCSP expression and function may be useful goals for targeted therapies for inhibition of the development of BPD.
Bronchopulmonary dysplasia (BPD) is recognized as an important cause of morbidity and mortality in preterm infants. Because the role of congenital infections in BPD has been debated, the purpose of this study was to test the hypothesis that detection of infectious agents in tracheal aspirate samples was associated with the development of BPD. Tracheal aspirate samples were obtained within the 1st week of life and screened by polymerase chain reaction for adenovirus, cytomegalovirus, parvovirus, enteroviruses, Ureaplasma urealyticum, Mycoplasma hominis, Mycoplasma pneumoniae, and Chlamydia species. BPD was defined as persistent oxygen dependence at 28 d of age and 36 wk postconceptional age (PCA). Infants that expired before these time points were excluded from statistical analysis. Out of 89 infants studied, at 28 d of life, 13 had expired, 45 had BPD, and 31 had no BPD (controls). At 36 wk PCA, 15 infants expired, 39 still had BPD, and 35 did not. A significant increase in the frequency of adenovirus genome was identified in BPD patients compared with controls, both at 28 d of life (12/45 = 27% versus 1/31 = 3%: p< or =0.01) and at 36 wk PCA (10/39 = 29% versus 2/35 = 6%: p = 0.01). Other microorganisms were rarely detected and not associated with the development of BPD. This is the first study reporting the frequency of detection of adenovirus DNA in tracheal aspirate samples obtained during the 1st week of life from infants with BPD and suggests that prenatal acquisition may be important in the development of BPD.
Because neutrophil attachment to endothelial cell adhesion molecules is a key event in the initiation of an inflammatory response, the association of higher early concentrations of soluble E-Selectin with the development of BPD suggests that E-Selectin may play a key role in the pathogenesis of lung inflammation and the development of BPD. This association also suggests that inflammatory events or effects leading to inflammatory responses occurring in the prenatal and/or very early perinatal periods contribute significantly to the pathogenesis of BPD.
Interferon gamma (IFN-gamma), a potent cytokine inducing a wide range of immunologic activities, is increased in the airway secondary to viral infection or during an inflammatory response. This increase in IFN-gamma concentration may alter the expression of specific airway epithelial cell genes that regulate adaptation of airway inflammatory responses. One protein induced by IFN-gamma is Clara cell secretory protein (CCSP), which may contribute to the attenuation of airway inflammation. This study was done to investigate the molecular mechanism by which IFN-gamma stimulates the expression of the CCSP gene in mouse transformed Clara cells and transgenic mice. Deletion mapping and linker-scanning mutations demonstrated that IFN-gamma-induced expression of CCSP was regulated, in part, at the level of transcription. In vitro and in vivo studies verified that the minimal IFN-gamma-responsive segment was localized to the proximal 166 bp of the 5'-flanking region. Additionally, IFN-gamma-induced expression of CCSP was mediated indirectly through an interferon regulatory factor-1-mediated increase in hepatocyte nuclear factor-3beta.
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