Human lung myofibroblast-derived inducers of alveolar epithelial apoptosis identified as angiotensin peptides.
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 alpha-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 microg/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].
Wang
R
R
The Cardiovascular Institute, Michael Reese Hospital, Chicago, Illinois 60616, USA.
Ramos
C
C
Joshi
I
I
Zagariya
A
A
Pardo
A
A
Selman
M
M
Uhal
B D
BD
D000804:Angiotensin II / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000808:Angiotensinogen / Q000235:genetics / Q000378:metabolism; D000906:Antibodies; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D002216:Captopril / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005355:Fibrosis; D005434:Flow Cytometry; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000201:enzymology / Q000473:pathology*; D012504:Saralasin / Q000494:pharmacology
D000806:Angiotensin-Converting Enzyme Inhibitors; D000906:Antibodies; D000808:Angiotensinogen; D000804:Angiotensin II; D002216:Captopril; D007703:Peptidyl-Dipeptidase A; D012504:Saralasin