title: Regulation of myofibroblast differentiation and bleomycin-induced pulmonary fibrosis by adrenomedullin.
abstract: Myofibroblast differentiation induced by transforming growth factor-β (TGF-β) is characterized by the expression of smooth muscle α-actin (SMA) and extracellular matrix proteins. We and others have previously shown that these changes are regulated by protein kinase A (PKA). Adrenomedullin (ADM) is a vasodilator peptide that activates cAMP/PKA signaling through the calcitonin-receptor-like receptor (CRLR) and receptor-activity-modifying proteins (RAMP). In this study, we found that recombinant ADM had little effect on cAMP/PKA in quiescent human pulmonary fibroblasts, whereas it induced a profound activation of cAMP/PKA signaling in differentiated (by TGF-β) myofibroblasts. In contrast, the prostacyclin agonist iloprost was equally effective at activating PKA in both quiescent fibroblasts and differentiated myofibroblasts. TGF-β stimulated a profound expression of CRLR with a time course that mirrored the increased PKA responses to ADM. The TGF-β receptor kinase inhibitor SB431542 abolished expression of CRLR and attenuated the PKA responses of cells to ADM but not to iloprost. CRLR expression was also dramatically increased in lungs from bleomycin-treated mice. Functionally, ADM did not affect initial differentiation of quiescent fibroblasts in response to TGF-β but significantly attenuated the expression of SMA, collagen-1, and fibronectin in pre-differentiated myofibroblasts, which was accompanied by decreased contractility of myofibroblasts. Finally, sensitization of ADM signaling by transgenic overexpression of RAMP2 in myofibroblasts resulted in enhanced survival and reduced pulmonary fibrosis in the bleomycin model of the disease. In conclusion, differentiated pulmonary myofibroblasts gain responsiveness to ADM via increased CRLR expression, suggesting the possibility of using ADM for targeting pathological myofibroblasts without affecting normal fibroblasts.
authors.affiliation: Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Kach
authors.forename: Nathan
authors.initials: N
authors.lastname: Sandbo
authors.forename: Nan
authors.initials: N
authors.lastname: Sethakorn
authors.forename: Jesse
authors.initials: J
authors.lastname: Williams
authors.forename: Eleanor B
authors.initials: EB
authors.lastname: Reed
authors.forename: Jennifer
authors.initials: J
authors.lastname: La
authors.forename: Xinyong
authors.initials: X
authors.lastname: Tian
authors.forename: Susan D
authors.initials: SD
authors.lastname: Brain
authors.forename: Kavitha
authors.initials: K
authors.lastname: Rajendran
authors.forename: Ramaswamy
authors.initials: R
authors.lastname: Krishnan
authors.forename: Anne I
authors.initials: AI
authors.lastname: Sperling
authors.forename: Konstantin
authors.initials: K
authors.lastname: Birukov
authors.forename: Nickolai O
authors.initials: NO
authors.lastname: Dulin
mesh_terms: D000199:Actins / Q000378:metabolism; D053607:Adrenomedullin / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001761:Bleomycin; D058286:Calcitonin Receptor-Like Protein / Q000096:biosynthesis; D002454:Cell Differentiation / Q000187:drug effects*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006801:Humans; D016285:Iloprost / Q000494:pharmacology; D051379:Mice; D058628:Myofibroblasts / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology*; D058263:Receptor Activity-Modifying Protein 2 / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D000199:Actins; D058286:Calcitonin Receptor-Like Protein; D058263:Receptor Activity-Modifying Protein 2; D016212:Transforming Growth Factor beta; D001761:Bleomycin; D053607:Adrenomedullin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D016285:Iloprost
keywords: PKA; TGF-β; adrenomedullin; fibrosis; myofibroblast