Human lung myofibroblast-derived inducers of alveolar epithelial apoptosis identified as angiotensin peptides

R Wang, C Ramos, I Joshi, A Zagariya… - … of Physiology-Lung …, 1999 - journals.physiology.org
R Wang, C Ramos, I Joshi, A Zagariya, A Pardo, M Selman, BD Uhal
American Journal of Physiology-Lung Cellular and Molecular …, 1999journals.physiology.org
Earlier work from this laboratory found that fibroblasts isolated from fibrotic human lung
[human interstitial pulmonary fibrosis (HIPF)] secrete a soluble inducer (s) of apoptosis in
alveolar epithelial cells (AECs) in vitro [BD Uhal, I. Joshi, A. True, S. Mundle, A. Raza, A.
Pardo, and M. Selman. Am. J. Physiol. 269 (Lung Cell. Mol. Physiol. 13): L819–L828, 1995].
The cultured human fibroblast strains most active in producing the apoptotic activity
contained high numbers of stellate cells expressing α-smooth muscle actin, a myofibroblast …
Earlier work from this laboratory found that fibroblasts isolated from fibrotic human lung [human interstitial pulmonary fibrosis (HIPF)] secrete a soluble inducer(s) of apoptosis in alveolar epithelial cells (AECs) in vitro [B. D. Uhal, I. Joshi, A. True, S. Mundle, A. Raza, A. Pardo, and M. Selman. Am. J. Physiol. 269 (Lung Cell. Mol. Physiol. 13): L819–L828, 1995]. The cultured human fibroblast strains most active in producing the apoptotic activity contained high numbers of stellate cells expressing α-smooth muscle actin, a myofibroblast marker. The apoptotic activity eluted from gel-filtration columns only in fractions corresponding to proteins. Western blotting of the protein fraction identified immunoreactive angiotensinogen (ANGEN), and two-step RT-PCR revealed expression of ANGEN by HIPF fibroblasts but not by normal human lung fibroblasts. Specific ELISA detected angiotensin II (ANG II) at concentrations sixfold higher in HIPF-conditioned medium than in normal fibroblast-conditioned medium. Pretreatment of the concentrated medium with purified renin plus purified angiotensin-converting enzyme (ACE) further increased the ELISA-detectable ANG II eightfold. Apoptosis of AECs in response to HIPF-conditioned medium was completely abrogated by the ANG II receptor antagonist saralasin (50 μg/ml) or anti-ANG II antibodies. These results identify the protein inducers of AEC apoptosis produced by HIPF fibroblasts as ANGEN and its derivative ANG II. They also suggest a mechanism for AEC death adjacent to HIPF myofibroblasts [B. D. Uhal,, I. Joshi, C. Ramos, A. Pardo, and M. Selman. Am. J. Physiol. 275 (Lung Cell. Mol. Physiol. 19): L1192–L1199, 1998].
American Physiological Society