INDUCTION OF INTERLEUKIN-1 AND INTERLEUKIN-8 MESSENGER-RNAS AND PROTEINS BY TGF-BETA(1) IN RAT LUNG ALVEOLAR EPITHELIAL-CELLS

The transforming growth factor-beta (TGF-beta) has been shown to incre ase in lung injury and in fibrotic states of the lung. In the current study, we sought to investigate whether TGF beta(1) induced the expres sion of IL-1 alpha and IL-8 in rat alveolar epithelial cells. We evalu ated TGF beta(1), IL-1 alpha, and IL-8 expression by immunofluorescenc e in silica-injured and saline-heated control rat lungs. Antibodies to IL-1 alpha, IL-8, and TGF beta(1) showed intense staining in silica-i njured lungs as compared to saline-instilled lungs. Primary isolated t ype II cells from silica-injured lungs showed increased expression of IL-1 alpha as compared to saline-instilled lungs. To evaluate the effe cts of TGF beta(1), we treated an immortalized rat type II cell-derive d cell line (LM5) with 100 pg/ml of TGF beta(1) in serum-free medium f or 0-24 hours and analyzed the expression of IL-1 alpha and IL-8 mRNAs and proteins using semiquantitative RT-PCR, Northern blot analysis, W estern blot analysis, and immunohistochemistry. Densitometric analysis of Northern blots showed modest constitutive expression of IL-1 alpha gene in untreated control LM5 cells. TGF beta(1) treatment resulted i n an increase in IL-1 alpha mRNA, that reached maximum levels (4-fold) by 2 hours and remained elevated for 4-16 hours, with a subsequent de cline by 24 hours. Similarly, Northern blot and RT-PCR analysis demons trated that TGF beta(1) treatment resulted in maximum induction of IL- 8 mRNA (6-8.5-fold) within 1-4 hours. The levels remained elevated for up to 24 hours afterwards. Western blot analysis results further conf irmed the expression of both IL-1 alpha and IL-8 proteins by LMS cells . TGF beta(1) treatment resulted in increased expression of both IL-1 alpha and IL-8 proteins. Immunofluorescence studies demonstrated incre ased staining of IL-1 alpha by TGF beta(1) as compared to untreated ce lls. These results suggest that TGF beta(1) may regulate IL-1 alpha an d IL-8 expression in alveolar epithelial cells and contribute to polym orphonuclear leukocyte recruitment and lung injury in clinical states with increased TGF beta(1). (C) 1996 Wiley-Liss, Inc.