Abstract 1460: Effect of HMR1766, a Soluble Guanylate Cyclase Activator, on Differentiation of Cardiac Fibroblasts and Extracellular Matrix Synthesis Induced by TGFbeta
Myocardial injury can trigger cardiac fibroblast proliferation, transformation into myofibroblasts and enhanced extracellular matrix production. The resulting cardiac fibrosis contributes to structural remodeling and ventricular dysfunction leading to heart failure. Cardiac release of ANP and BNP, which stimulate guanylyl cyclase linked receptors with the subsequent rise in cGMP have been reported to inhibit cardiac fibrosis. cGMP can be also synthesized by cytosolic NO-sensitive guanylyl cyclases. HMR1766 is the first member of a new class of soluble guanylyl cyclase activators acting preferentially on the oxidized form of the enzyme in an NO-independent manner. Experiments were designed to study the effect of this compound on TGFβ-induced cardiac fibroblast extracellular matrix (ECM) synthesis and differentiation. HMR1766 (0.3–3 μM) induced a time dependent increase of cGMP (maximum 630 %) in rat cardiac ventricular fibroblasts in the presence of IBMX (100 μM). Using these cells, a specific model of ECM synthesis was developed based on [3H]proline incorporation in ECM of fibroblasts treated for 5 days with ascorbic acid (50 μg/ml). TGFβ (25 ng/ml) produced a marked increase in ECM synthesis (250 %) which was significantly inhibited by increasing concentrations of HMR1766 (0.3–10 μM). Similar results were obtained when the cells were treated with a NO donor, SIN1 (10–1000 μM). Cardiac fibroblast differentiation into myofibroblasts induced by TGFβ was evaluated using RT-PCR (collagen type I, fibronectin EIIIA, CGTF) and Western Blots of alpha smooth muscle actin and fibronectin EIIIA. In the presence of IBMX, HMR1766 (0.3 to 3 μM) did not modify mRNA expression but inhibited fibronectin protein synthesis in a concentration dependent manner. In conclusion, HMR1766, a novel guanylate cyclase activator, inhibits overall matrix synthesis induced by TGFβ in cardiac fibroblasts and inhibits the diffentiation of fibroblasts into myofibroblasts. Thus, HMR1766, in complement to its haemodynamic properties, may have an additional beneficial effect on cardiac fibrosis.