Angiotensin II has multiple profibrotic effects in human cardiac fibroblasts

Background-Angiotensin II (Ang II) is implicated in cardiac remodeling and is increasingly recognized for its profibrotic activity. Methods and Results-Because little is known about the direct cellular effec ts of Ang II on human cardiac fibroblasts, we isolated fibroblasts from ven tricles of explanted human hearts and added Ang II (100 nmol/L) to determin e its role in growth, extracellular matrix accumulation, and adhesion. To a ssess which Ang II receptor is involved, Ang II was added in the presence o f irbesartan (10 mu mol/L), a specific AT(1) receptor antagonist; PD 123319 (10 mu mol/L,), a specific AT(2) receptor antagonist, or divalinil (100 nm ol/L), an AT(4) receptor inhibitor. In human ventricles (n=13), message lev els of atrial natriuretic peptide and AT(1) receptor were inversely correla ted, which suggests a decrease in AT(1) receptor expression with progressiv e heart failure. Northern analysis and fluorescence-activated cell sorting demonstrated AT(1) receptor in cultured human cardiac fibroblasts. Ang II i ncreased mitogen-activated protein kinase activity and in DNA synthesis (5- fold, P<0.01) stimulated a 2-fold increase in transforming growth factor-be ta(1) (P<0.05) mRNA levels at 2 hours and a 2-fold increase in laminin (P<0 .05) and fibronectin (P<0.05) mRNA levels at 24 hours. Ang II also enhanced plasminogen activator inhibitor-1 expression, which inhibits metalloprotei nases that degrade the extracellular matrix. All of these effects were inhi bited by irbesartan but not PD 123319 or divalinil. In addition, Ang II inc reased cardiac fibroblast attachment to collagens I and III, which was asso ciated with an increase in focal adhesion kinase activity. Conclusions-Activation of the AT(1) receptor in human heart promotes fibros is. Ang II plays a novel role in stimulation of plasminogen activator inhib itor-1 expression and adhesion of cardiac fibroblasts to collagen.