Abstract 20793: Prostaglandin EP4 Signaling Negatively Regulates Vascular Elastic Fiber Assembly in the Ductus Arteriosus
Introduction: Elastic fiber formation is essential for elasticity of arteries. However, the hormonal regulation of elastic fiber formation remains largely unknown. Because the ductus arteriosus (DA), where prostaglandin E receptor, EP4, is highly expressed, exhibits hypoplastic elastic fiber formation, we hypothesized that EP4 signaling inhibits elastic fiber formation in arteries.
Methods: Pooled tissues from the rat DA and the aorta were used for RT-PCR. Protein expression and elastolytic activity were assessed by immunoblotting and elastin-zymography, respectively. Smooth muscle cells (DASMCs) was obtained from the rat DA.
Results: Elastica staining, immunostaining and electron microscopy studies showed that elastic fiber was less formed in the DA compared to the aorta (0.56-fold, P<0.01, n=6). The expression level of lysyl oxidase (LOX) mRNA that catalyzes cross-links in elastin was lower in the DA tissue than in the aorta (0.52-fold, P<0.01, n=8). A selective EP4 agonist, ONO-AE1-329, significantly decreased LOX mRNA and protein (0.18-and 0.25-fold, P<0.01, n=6) in DASMCs, but EP1/3 (sulprostone) or EP2 agonist (butaprost) did not. An EP4 agonist decreased phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in DASMCs. An ERK1/2 inhibitor, U0126, decreased LOX expression. Immunocytochemistry showed that an EP4 agonist attenuated elastic fiber formation of DASMCs, but EP1/3 or EP2 agonist did not. Adenovirus-mediated overexpression of LOX rescued EP4-mediated disruption of elastic fiber formation. EP4 agonist increased elastolytic matrix metalloproteinase-2 (MMP-2) activity in DASMCs. When EP4 was disrupted in mice, elastic fiber formation was increased in the DA. More importantly, human coarctation of the aorta showed disrupted elastic fiber formation and increased EP4 expression.
Conclusion: These results suggest that EP4 signaling inhibits vascular elastic fiber formation through attenuation of LOX-mediated cross-linking of elastic fiber and MMP-2-mediated degradation of elastin. Pharmacological inhibition of EP4 signaling may be a novel strategy for treating abnormal elastic fiber formation, such as coarctation of the aorta, in which no effective pharmacological therapy has been available.
- © 2010 by American Heart Association, Inc.