Expression of transforming growth factor-beta receptors during hyperoxia-induced lung injury and repair.

Lung injury and repair processes involve many cellular activities, including cell growth, differentiation, and remodeling of extracellular matrix components. Transforming growth factor-beta (TGF-beta) is a major class of signaling peptide growth factors regulating these cellular activities. Type I (T beta RI) and type II (T beta RII) receptors for TGF-beta are transmembrane serine/threonine kinases that are essential for TGF-beta signaling. To gain insight into the possible molecular mechanisms of lung injury and repair, we investigated the expression of T beta RI and T beta RII in an acute hyperoxia-induced model of lung injury and repair. Localization of message expression of T beta RI and T beta RII in oxygen-exposed rat lung tissue was analyzed by using in situ hybridization. T beta RI mRNA expression was found in the interstitium, capillaries, and the alveolar septa of rat lungs exposed for 60 h to 100% oxygen. The distribution of T beta RII mRNA in oxygen-exposed rat lung tissue overlapped the localization of T beta RI mRNA. Temporal changes of T beta RI and T beta RII mRNA expressions in rat lung during hyperoxic exposure and repair were examined by Northern analysis. We found that expression of T beta RI was upregulated in adult rats undergoing prolonged exposure to 100% oxygen, and the increase of T beta RI expression persisted during 2 wk of repair of lung injury. The pattern of T beta RII expression during hyperoxic exposure and repair was distinct from that of T beta RI. The expression of T beta RII increased with a peak at 3 days postexposure and then declined after 7 days of repair. Changes of T beta RI and T beta RII protein expressions in rat lung during hyperoxic exposure and repair were examined further by Western blot analysis, which correlated with the mRNA expression. The results suggest that T beta RI and T beta RII may play important roles during the lung injury and repair by mediating signaling activity of TGF-beta and may regulate interactions between the mesenchyme and the epithelium.