Published ahead of print on July 13, 2007, doi:10.1165/rcmb.2006-0379TR Am. J. Respir. Cell Mol. Biol., Volume 37, Number 6, December 2007, 640-650 A more recent version of this article appeared on December 1, 2007
Submitted on October 9, 2006 The Angiotensin II Receptor 2 is Expressed and Mediates Angiotensin II Signalling in Lung FibrosisMelanie Konigshoff1*,1 Department of Medicine, University of Giessen Lung Center, Giessen, Germany, 2 Department of Radiotherapy and Oncology, Philipps-University Marburg, Marburg, Germany * To whom correspondence should be addressed. E-mail: melanie.koenigshoff{at}innere.med.uni-giessen.de.
Idiopathic Pulmonary Fibrosis (IPF) is a severe interstitial lung disease unresponsive to currently available therapies. In IPF, initial alveolar epithelial cell damage leads to fibroblast-(myo)fibroblast activation, which deposit an increased amount of a collagen-rich extracellular matrix (ECM). Angiotensin II (ANGII) signalling, mediated via angiotensin II receptor type 1 (AGTR1) or type-2 (AGTR2), controls tissue remodelling in fibrosis, but the relevance of AGTR2 remains elusive. In the present study, we demonstrated increased expression of AGTR1 und AGTR2 in human and rodent lung tissues from IPF patients and mice subjected to bleomycin-induced fibrosis, respectively. Both AGTR1 und AGTR2 localized to interstitial fibroblasts. Quantitative analysis of cell-surface expression in primary mouse fibroblasts revealed a significant increase of AGTR2 surface expression in fibrotic fibroblasts, whereas AGTR1 surface expression levels remained similar. ANGII treatment of normal fibroblasts led to enhanced migration and proliferation, which was abrogated after pretreatment with losartan (LOS), an AGTR1 inhibitor. In contrast, in fibrotic fibroblasts, migration and proliferation was modified only by AGTR2, but not AGTR1 inhibition (using PD123319). ANGII-induced effects were mediated via phosphorylation of the MAP kinases p38 and p42/44, which was blocked via LOS and PD, respectively. Similar effects of AGTR1 and AGTR2 inhibition were observed using conditioned media of alveolar epithelial cells, a prominent source of ANGII in the lung in vivo. In summary, we conclude that ANGII signalling occurs primarily via AGTR1 in normal fibroblasts, while AGTR2-mediated effects are dominant on activated (myo)-fibroblasts, a receptor switch that may perturb epithelial-mesenchymal interaction, thereby further perpetuating fibrogenesis.
This article has been cited by other articles:
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||