title: Endothelin-converting enzyme-1 gene ablation attenuates pulmonary fibrosis via CGRP-cAMP/EPAC1 pathway.
abstract: Endothelin-1 (ET-1) has been shown to be involved in human pulmonary fibrosis. However, recent clinical trials targeting the ET-1 pathway with ET-1 receptor antagonists failed to achieve beneficial outcomes. Another strategy opposing the actions of ET-1 involves the inhibition of endothelin-converting enzyme-1 (ECE-1). We hypothesize that ECE-1 inhibition exerts beneficial effects on pulmonary fibrosis. Pulmonary fibrosis was induced by instilling bleomycin intratracheally into ECE-1 heterozygous knockout mice (ECE-1(+/-)) and their wild-type control mice (ECE-1(+/+)). Lung inflammation and fibrosis were assessed on Days 7, 14, and 28 after bleomycin instillation. The activity of ECE-1 and the concentrations of its related peptides, ET-1, bradykinin, atrial natriuretic peptide (ANP), and calcitonin gene-related peptide (CGRP), were determined. ECE-1(+/-) mice demonstrated less lung inflammation and limited fibrosis compared with control mice. ECE-1 activity was half-reduced in ECE-1(+/-) mice, and this activity also altered ET-1 and CGRP concentrations, but not concentrations of bradykinin and ANP. ET-1 concentrations were found to be lower in ECE-1(+/-) mice after the development of fibrosis, in contrast to the unaltered concentrations during inflammation. Reduced ECE-1 activity resulted in higher CGRP concentrations, which altered the pathological functionality of the lung, indicating the activation of the CGRP pathway involving cyclic adenosine monophosphate (cAMP)/exchange protein directly activated by cAMP and cAMP/protein kinase A in ECE-1(+/-) mice. Bleomycin instillation on Day 14 induced the accumulation of M2 macrophages expressing CGRP receptors in ECE-1(+/-) mice. Our results emphasize that the in vivo ECE-1-mediated degradation of CGRP promotes the transition from lung inflammation to fibrosis. Further, our study identified M2 macrophages as the target cells of CGRP action during this transition.
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Anggoro Budi
authors.initials: AB
authors.lastname: Hartopo
authors.forename: Noriaki
authors.initials: N
authors.lastname: Emoto
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vignon-Zellweger
authors.forename: Yoko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Keiko
authors.initials: K
authors.lastname: Yagi
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakayama
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hirata
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000009:adverse effects / Q000494:pharmacology; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D001761:Bleomycin / Q000009:adverse effects / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D017353:Gene Deletion; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D059748:Proteolysis / Q000187:drug effects; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction
chemical_list: D000903:Antibiotics, Antineoplastic; C482601:Epac protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D001761:Bleomycin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; C000606923:ECE1 protein, human; C000606925:Ece1 protein, mouse; D000072396:Endothelin-Converting Enzymes; D015740:Calcitonin Gene-Related Peptide