TEMPORAL CHANGES IN EXPRESSION OF TGF-BETA ISOFORMS IN MOUSE LUNG EXPOSED TO OXYGEN

Oxygen-induced pulmonary injury is associated with cell death and a si gnificant inflammatory response. Because transforming growth factor (T GF)-beta is a potent modulator of the immune response, changes in expr ession of the three TGF-beta (beta 1, beta 2, beta 3) isoforms was det ermined in lungs of adult mice exposed to >95% oxygen. TGF-beta 1 immu nostaining within cuboidal non-ciliated bronchiolar epithelial cells w as increased within 3 h of oxygen exposure and continued to increase f or 48 h before decreasing to control levels by 72 h. A similar but les s marked change that was morphologically consistent with alveolar type II cells was observed in granulated cells. Immunostaining for TGF-bet a 2 and TGF-beta 3 revealed a similar change in bronchiolar epithelium with little change observed in the alveolar epithelium. Immunohistoch emical changes in TGF-beta expression were not observed in any other p ulmonary cells. Northern blot analysis of total lung RNA revealed that expression of the TGF-beta mRNA was not markedly altered over the 72- h exposure period. Exposure to >95% oxygen resulted in cell type-speci fic posttranscriptional changes in TGF-beta isoforms in the lung.