Abstract 16136: Anti-fibrotic Effect of Prostaglandin E2-EP4 in the Heart
Introduction: Cardiac fibrosis leads to heart failure, which is not curable with current therapy. Previously, we have shown that cyclic AMP signaling attenuated cardiac fibrosis through inhibiting transformation of quiescent fibroblasts to active myofibroblasts. Although it is well known that prostaglandin E2 (PGE2) receptor EP4 acts via cyclic AMP and is abundantly expressed in the heart, the role of EP4 in cardiac fibrosis is not fully understood. We assessed the hypothesis that PGE2-EP4 signaling inhibits cardiac fibrosis.
Methods: Cardiac fibroblasts (CFs) and cardiomyocytes (CMs) were isolated from global knockout of EP4 (EP4+/-) and EP4+/+ male littermate mice (3 month-old) or 5 week-old male rats by Langendorff collagenase perfusion. CFs were stimulated with the EP4 agonist CAY 10589 at 1μM for 48h. Expression levels of mRNA of myofibroblast markers, such as α-smooth muscle actin (αSMA) and connective tissue growth factor (CTGF) were assessed by quantitative RT-PCR. Western blotting was used to examine protein expression. We generated mice overexpressing EP4 only in CMs (CM-EP4TG) using the Cre-loxP system under SM22 promoter. Cardiac fibrosis was induced by 7 day-infusion of angiotensin II (ATII) (1.0μg/kg/min) and was assessed by picrosirius red stain in EP4+/- and CM-EP4TG.
Results: EP4 mRNA was predominantly expressed in CFs compared to CMs in EP4+/+ heart (9.3±0.1-fold, n=4, p<0.05). In EP4+/- CFs where expression of EP4 mRNA was decreased (0.58±0.01-fold vs. EP4+/+, n=7, p<0.05), mRNA expressions of αSMA and CTGF were higher compared to EP4+/+ CFs (2.1±0.4-fold, p<0.05, and 1.6±0.2-fold, p=0.07, respectively, n=5). Systemic administration of ATII-induced cardiac fibrosis was greater in EP4+/- than in EP4+/+ mice (4.6±1.7-fold, n=4, p<0.05), while ATII-induced fibrosis was similarly observed in both non-transgenic and CM-EP4TG mice. Furthermore, stimulation of EP4 decreased CTGF protein expression in culture supernatant of rat CFs (0.69±0.1-fold, n=4, p<0.05).
Conclusions: Endogenous PGE2-EP4 signaling has protective roles against cardiac fibrosis possibly through inhibiting CTGF-mediated activation of myofibroblasts. Stimulation of EP4 may be a new therapeutic strategy to prevent excessive cardiac fibrosis.
- © 2013 by American Heart Association, Inc.