Abstract 981: S1P-Stimulated Cardiac Fibrosis is Attenuated by a Novel Anti-S1P Monoclonal Antibody
Following myocardial infarction (MI) cardiac fibroblasts (CF) proliferate, undergo transformation into myofibroblasts and produce increased amounts of extracellular matrix (ECM). Increased ECM production by CF results in perivascular and interstitial fibrosis leading to diastolic dysfunction by increasing myocardial stiffening, impairing ventricular filling and thus reducing cardiac output. Sphingosine-1-phosphate (S1P), a bioactive lysophospholipid, regulates cardiac myocyte (CM) hypertrophy and survival; however very little is known regarding S1P-mediated effects on CF function after MI. We hypothesized that S1P stimulates proliferation, myofibroblast transformation and collagen production by CF and thereby promotes maladaptive fibrosis during cardiac remodeling after MI. Quantitative real-time PCR analysis of ventricular CF and CM isolated from adult mouse revealed that expression of sphingosine kinase 1 and 2 and S1P 3 receptor expression is greater in CF compared to CM, suggesting increased S1P production and signaling in CF. S1P enhanced CF proliferation (3.1±1.2 fold*) in an ERK dependent manner and increased α-smooth muscle actin (a myofibroblast marker) expression and collagen production by 2.2±0.2* and 1.6±0.04* fold, respectively. These effects paralleled increased Rho activation (1.6±0.2 fold*) and were abolished by a Rho kinase inhibitor (Y-27632). To study the role of S1P in cardiac fibrosis post-MI, we employed a novel, monoclonal antibody to S1P (anti-S1P mAb) which sequesters circulating S1P. Intraperitoneal (IP) administration of the anti-S1P mAb dramatically attenuated macrophage and mast cell infiltration into the infarct zone at day 4 and reduced perivascular fibrosis within the non-infarcted myocardium by 65±15%* at 2 weeks. In conclusion, these findings demonstrate that S1P stimulates CF proliferation, differentiation and function thereby contributing to cardiac fibrosis after MI. Thus, the anti-S1P mAb may provide a means to reduce circulating S1P levels thus attenuating inflammatory cell infiltration and deleterious connective tissue production during cardiac remodeling. *Values are expressed as average ± SEM, n≥3 and p&;e;0.05.