ABSTRACT
<p><b>BACKGROUND</b>Many studies have suggested that angiotensin II (Ang II) and its receptors may be involved in the development of asthma. However, the expression of angiotensin II receptors (AGTR) is not clear in the lung tissue of chronic asthmatics. This study was designed to determine the relationship between airway remodeling, dysfunction and the expression of AGTRs in a rat model of asthma.</p><p><b>METHODS</b>Rats were sensitized with ovalbumin (OVA) for 2 weeks. Sixty minutes before an inhalation challenge, the rats were pretreated either with valsartan (15, 30, 50 mg x kg(-1) x d(-1)) or saline intragastrically. Then the rats received an OVA challenge for 30 alternative days. Acetylcholine (Ach)-induced bronchoconstriction was measured after the final antigen challenge. White cell counts in bronchoalveolar lavage fluid (BALF) and morphological changes in the airways were then assessed. The levels of transforming growth factor-beta 1 (TGF-beta(1)) and platelet-derived growth factor (PDGF) in BALF were detected by ELISA. The levels of AGTR1 and AGTR2 mRNA and protein in lung tissues were measured by RT-PCR and Western blotting.</p><p><b>RESULTS</b>AGTR1 mRNA and protein levels in repeatedly OVA-challenged rats were significantly increased as compared with negative controls. The AGTR1 mRNA expression versus white cell counts of BALF and airway wall thickness (mainly in small airways) in lungs of chronic antigen-exposed rats were positively correlated. Valsartan decreased the level of AGTR1 in repeatedly OVA-challenged rats. However, AGTR2 mRNA and protein levels in the OVA-challenged rats and high-dose valsartan-treated rats (50 mg x kg(-1) x d(-1)) were also increased. Valsartan significantly decreased inflammatory cell accumulation and attenuated Ach-evoked bronchoconstriction in repeatedly antigen-challenged rats. Valsartan also decreased allergen-induced structural changes in rat airway (including total airway wall thickness and smooth muscle area) and the levels of TGF-beta(1) and PDGF in BALF.</p><p><b>CONCLUSIONS</b>AGTR1 expression is potentially associated with airway remodeling and dysfunction in asthma. Ang II and AGTR1 may participate in airway inflammation and airway remodeling of chronic antigen-exposed rats. Valsartan, a AGTR1 antagonist, could inhibit AGTR1 expression and partially inhibits structural airway changes as well as airway inflammation in chronic OVA-exposed rats.</p>