title: Abrogation of ER stress-induced apoptosis of alveolar epithelial cells by angiotensin 1-7.
abstract: Earlier work showed that apoptosis of alveolar epithelial cells (AECs) in response to endogenous or xenobiotic factors is regulated by autocrine generation of angiotensin (ANG) II and its counterregulatory peptide ANG1-7. Mutations in surfactant protein C (SP-C) induce endoplasmic reticulum (ER) stress and apoptosis in AECs and cause lung fibrosis. This study tested the hypothesis that ER stress-induced apoptosis of AECs might also be regulated by the autocrine ANGII/ANG1-7 system of AECs. ER stress was induced in A549 cells or primary cultures of human AECs with the proteasome inhibitor MG132 or the SP-C BRICHOS domain mutant G100S. ER stress activated the ANGII-generating enzyme cathepsin D and simultaneously decreased the ANGII-degrading enzyme ACE-2, which normally generates the antiapoptotic peptide ANG1-7. TAPI-2, an inhibitor of ADAM17/TACE, significantly reduced both the activation of cathepsin D and the loss of ACE-2. Apoptosis of AECs induced by ER stress was measured by assays of mitochondrial function, JNK activation, caspase activation, and nuclear fragmentation. Apoptosis induced by either MG132 or the SP-C BRICHOS mutant G100S was significantly inhibited by the ANG receptor blocker saralasin and was completely abrogated by ANG1-7. Inhibition by ANG1-7 was blocked by the specific mas antagonist A779. These data show that ER stress-induced apoptosis is mediated by the autocrine ANGII/ANG1-7 system in human AECs and demonstrate effective blockade of SP-C mutation-induced apoptosis by ANG1-7. They also suggest that therapeutic strategies aimed at administering ANG1-7 or stimulating ACE-2 may hold potential for the management of ER stress-induced fibrotic lung disorders.
authors.affiliation: Department of Physiology, Michigan State University, 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: Hang
authors.initials: H
authors.lastname: Nguyen
authors.forename: MyTrang
authors.initials: M
authors.lastname: Dang
authors.forename: Indiwari
authors.initials: I
authors.lastname: Gopallawa
authors.forename: Jing
authors.initials: J
authors.lastname: Jiang
authors.forename: Vinh
authors.initials: V
authors.lastname: Dang
authors.forename: Shinji
authors.initials: S
authors.lastname: Ono
authors.forename: Konosuke
authors.initials: K
authors.lastname: Morimoto
mesh_terms: D000803:Angiotensin I / Q000494:pharmacology*; D000804:Angiotensin II / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists / Q000494:pharmacology; D000959:Antihypertensive Agents / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D019898:Autocrine Communication; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000473:pathology; D037721:Pulmonary Surfactant-Associated Protein C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011945:Receptors, Angiotensin / Q000737:chemistry; D015398:Signal Transduction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D057911:Angiotensin Receptor Antagonists; D000959:Antihypertensive Agents; D000970:Antineoplastic Agents; D007976:Leupeptins; D010446:Peptide Fragments; D037721:Pulmonary Surfactant-Associated Protein C; D011945:Receptors, Angiotensin; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D000803:Angiotensin I; C118790:angiotensin I (1-7); C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: ADAM17/TACE; BRICHOS domain mutations; idiopathic pulmonary fibrosis; substituted peptide receptor antagonists