Angiotensin II Stimulated Expression of Transforming Growth Factor-β1in Cardiac Fibroblasts and Myofibroblasts

Angiotensin II (Ang II) stimulates pathologic myocardial fibrosis. Cardiac fibroblasts (CFb) and myofibroblasts mediate this response, perhaps in part by indirect production of specific cytokines. We sought to determine if Ang II could stimulate transforming growth factor-β1(TGF-β1) gene expression and protein production in adult rat CFb and two cardiac myofibroblast cell types, scar myofibroblasts (MyoFb) and valvular interstitial cells (VIC). Confluent CFb, MyoFb, and VIC in serum-deprived (0.4% FCS) media were treated with Ang II (10−7 for CFb; 10−9 for MyoFb, VIC) for 24 h. Untreated cells served as controls. Culture media was collected and TGF-β1levels determined in triplicate using a sandwich ELISA. Reverse transcriptase–polymerase chain reaction (RT–PCR) analysis was performed to determine TGF-β1mRNA expression. Ang II increased CFb (P<0.02) and VIC (P<0.04) TGF-β1mRNA expression, while the increase in MyoFb was not statistically significant. MyoFb produced the highest TGF-β1levels under control conditions compared to VIC and CFb. Ang II stimulated further TGF-β1secretion in VIC and CFb, but not MyoFb. The AT1receptor antagonist Losartan (10−7 ) greatly attenuated Ang II-stimulated TGF-B1secretion and decreased TGF-β1immunostaining in VIC. The AT2receptor antagonist PD123177 (10−7 ) also decreased secretion and immunostaining of TGF-β1in VIC, but to a lesser extent than Losartan. TGF-β1secretion by MyoFb was unaffected by Losartan and PD123177, although TGF-B1immunostaining was absent or greatly decreased, respectively, compared to Ang II-treated MyoFb. Ang II stimulates TGF-β1gene expression and/or protein production in cardiac fibroblast-like cells which may act as an autocrine/paracrine stimulus to collagen formation. Furthermore, TGF-β1production and secretion in these cells can be modulated by specific Ang II receptor antagonists, suggesting a potential benefit in preventing/attenuating pathologic myocardial fibrosis.