title: Regulation of alveolar epithelial cell survival by the ACE-2/angiotensin 1-7/Mas axis.
abstract: Earlier work from this laboratory demonstrated that apoptosis of alveolar epithelial cells (AECs) requires autocrine generation of angiotensin (ANG) II. More recent studies showed that angiotensin converting enzyme-2 (ACE-2), which degrades ANGII to form ANG1-7, is protective but severely downregulated in human and experimental lung fibrosis. Here it was theorized that ACE-2 and its product ANG1-7 might therefore regulate AEC apoptosis. To evaluate this hypothesis, the AEC cell line MLE-12 and primary cultures of rat AECs were exposed to the profibrotic apoptosis inducers ANGII or bleomycin (Bleo). Markers of apoptosis (caspase-9 or -3 activation and nuclear fragmentation), steady-state ANGII and ANG1-7, and JNK phosphorylation were measured thereafter. In the absence of Bleo, inhibition of ACE-2 by small interfering RNA or by a competitive inhibitor (DX600 peptide) caused a reciprocal increase in autocrine ANGII and corresponding decrease in ANG1-7 in cell culture media (both P < 0.05) and, moreover, induced AEC apoptosis. At baseline (without inhibitor), ANG1-7 in culture media was 10-fold higher than ANGII (P < 0.01). Addition of purified ANGII or bleomycin-induced caspase activation, nuclear fragmentation, and JNK phosphorylation in cultured AECs. However, preincubation with ANG1-7 (0.1 μM) prevented JNK phosphorylation and apoptosis. Moreover, pretreatment with A779, a specific blocker of the ANG1-7 receptor mas, prevented ANG1-7 blockade of JNK phosphorylation, caspase activation, and nuclear fragmentation. These data demonstrate that ACE-2 regulates AEC survival by balancing the proapoptotic ANGII and its antiapoptotic degradation product ANG1-7. They also suggest that ANG1-7 inhibits AEC apoptosis through the ANG1-7 receptor mas.
authors.affiliation: Dept. of Physiology, Michigan State Univ., 3197 Biomedical and Physical Sciences Bldg., East Lansing, MI 48824, USA. uhal@msu.edu
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Uhal
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Li
authors.forename: Anita
authors.initials: A
authors.lastname: Xue
authors.forename: Xu
authors.initials: X
authors.lastname: Gao
authors.forename: Amal
authors.initials: A
authors.lastname: Abdul-Hafez
mesh_terms: D000803:Angiotensin I / Q000502:physiology*; D000085962:Angiotensin-Converting Enzyme 2; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D010446:Peptide Fragments / Q000502:physiology*; D007703:Peptidyl-Dipeptidase A / Q000502:physiology*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000166:cytology; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*
chemical_list: D010446:Peptide Fragments; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D043562:Receptors, G-Protein-Coupled; D001761:Bleomycin; D000803:Angiotensin I; D007703:Peptidyl-Dipeptidase A; C000705307:ACE2 protein, human; C000705328:Ace2 protein, mouse; C000705329:Ace2 protein, rat; D000085962:Angiotensin-Converting Enzyme 2; C118790:angiotensin I (1-7)