Respiratory distress syndrome/bronchopulmonary dysplasia (RDS/BPD) represent the most common cause of mortality and morbidity in the premature infant. Although the cause of RDS has been established to be immaturity of the pulmonary surfactant system, the etiology of BPD is probably multifactorial and certainly ill defined. There exists a number of indirect observations which implicate oxyradicals in the pathogenesis of BPD, however direct evidence linking oxyradical macromolecular injury and clinical development of BPD is meager at best. The overall goal of Project #1 in this SCOR proposal is to provide direct evidence of oxyradical macromolecular injury in infants during the acute phase of BPD. Furthermore, this investigation will examine oxyradical injury toward cultured alveolar type II pneumocytes as a BPD model of in vitro oxyradical injury. The clinical aspect of this investigation will analyze both endotracheal aspirate, as well as plasma samples from intubated, cannulated premature infants with RDS during the during development of acute BPD. These samples will be fractionated and analyzed for their fatty acid profiles (including perhydroxyl derivatives of polyunsaturated fatty acids), malondialdehyde and vitamin E isomers utilizing the techniques of high performance liquid chromatography and gas chromatograph/mass spectroscopy. Endotracheal aspirates will additionally be serially assessed for protein concentration and myeloperoxidase activity, and phospholipid binding protein and surfactant associated protein A as markers for inflammation and type II cell alteration respectively. Infants enrolled In the clinical study will be nutritionally supplemented with vitamin E and polyunsaturated fatty acids to normalize these constituents so that these variables will be controlled. Severity of illness in these infants will be determined by a number of validated clinical scoring systems, while BPD will be diagnosed on day 21 of life utilizing clinical and radiographic criteria. In addition to the clinical studies a series of experiments involving oxyradical stress on cultured alveolar type II pneumocytes will also be pursued. These investigations will examine the.potential of various oxidant stresses (hydrogen peroxide, glucose oxidase, xanthine oxidase, neutrophils. hyperoxia) to mediate macromolecular (lipid, protein, nucleic acid) injury. Analyses of lipid peroxidation products will be performed in a fashion identical to the clinical investigation. Determination of sulfhydryl redox state will reflect oxygen stress toward type II cell protein while sensitive analyses of DNA conformation will reveal oxidant damage towards nucleic acid. Susceptibility towards oxyradical stress in cultured adult type 11 cells will be compared to that of fetal type II cells. Utilizing the combined approach of clinical as well as cell culture studies the investigators expect to provide direct evidence that oxyradicals are associated with the pathogenesis of BPD.
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