PULMONARY SURFACTANT SYSTEM & RADIATION PNEUMONITIS

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The central concept of this research proposal is to develop sensitive and reproductible biochemical assays of radiation- induced lung damage in in vivo and in vitro models which are applicable to man, and to study the effects of radiation-induced alterations. The major focus of our investigations will shift to a search for biochemical markers of different target cells in addition to Type II alveolar pneumocytes and to find predictors for both later effects--pneumonitis and fibrosis. There are basic structural changes in type II pneumocytes and immediate biochemical alterations following radiation exposure of lung tissue that can lead to pneumonitis and have a potential to be utilized as diagnostic tools. In our three different murine models and a rabbit model, we found a slight dissociation of surfactant release, ususally at slightly lower doses, from lethality. The concept of quantification of pulmonary surfactant release by an apoprotein rather than a phospholipid will be coupled with newer techniques to measure and analyze for other proteins using two-dimensional gel electrophoresis and immunochemical analyses. Furthermore, a panel of monoclonal antibodies directed against surface antigens of the adult type II pneumocyte have been characterized and these will be constructed and utilized in examination of the lavage and, since some of these products do enter extracellular spaces and may gain access to the blood, serum samples. Preliminary studies have shown detection of the apoprotein antigen in the blood of exposed animals in direct proportion to the severity of the exposure. The expsure refers to non-radiation injury produced by nitrogen dioxide, oxygen, hyperoxia and oleic acid and will be repeated with radiation. A new direction of investigation will be to study the effects of radiation directly on the nucleus and genetic function of type II pneumocytes. An attempt will be made to correlate the cellular changes of type II cells with altered gene expression of surfactant synthesis. As a preliminary step to human studies following lung irradiation, serial lavaging in the clinic has been initiated to develop quantitative techniques to determine the alveolar surface being lavaged and a lung lavage profile of different biochemical factors that may act as predictors for either later pneumonitis or fibrosis.