Angiotensin-(1-7) attenuates airway remodelling and hyperresponsiveness in a model of chronic allergic lung inflammation

Abstract

Background and Purpose A long-term imbalance between pro- and anti-inflammatory mediators leads to airway remodelling, which is strongly correlated to most of the symptoms, severity and progression of chronic lung inflammation. The Angiotensin-(1-7) [Ang-(1-7)]/Mas receptor axis of the renin-angiotensin system is associated with attenuation of acute and chronic inflammatory processes. In this study, we investigated the effects of Ang-(1-7) treatment in a model of chronic allergic lung inflammation. Experimental Approach Mice were sensitized to ovalbumin (OVA; 4 injections over 42 days, 14 days apart) and were challenged three times per week (days 21-46). These mice received Ang-(1-7) (1 μg·h-1, s.c.) by osmotic mini-pumps, for the last 28 days. Histology and morphometric analysis were performed in left lung and right ventricle. Airway responsiveness to methacholine, analysis of Ang-(1-7) levels (RIA), collagen I and III (qRT-PCR), ERK1/2 and JNK (Western blotting), IgE (elisa), cytokines and chemokines (elisa multiplex), and immunohistochemistry for Mas receptors were performed. Key Results Infusion of Ang-(1-7) in OVA-sensitized and challenged mice decreased inflammatory cell infiltration and collagen deposition in the airways and lung parenchyma, and prevented bronchial hyperresponsiveness. These effects were accompanied by decreased IgE and ERK1/2 phosphorylation, and decreased pro-inflammatory cytokines. Mas receptors were detected in the epithelium and bronchial smooth muscle, suggesting a site in the lung for the beneficial actions of Ang-(1-7). Conclusions and Implications Ang-(1-7) exerted beneficial attenuation of three major features of chronic asthma: lung inflammation, airway remodelling and hyperresponsiveness. Our results support an important protective role of Ang-(1-7) in lung inflammation.