Abstract 20249: Activation Of EGFR/p38 /JNK Pathway Contribute To Oxygen-induced Contraction Of Ductus Arteriosus
Introduction: Failure of the ductus arteriosus (DA) to close after birth results in a condition called patent ductus arteriosus, which is a relatively common congenital heart defect in premature neonates. Contraction of the ductus arteriosus is initiated at birth by both calcium influx and Rho-kinase activation, which leads to an increase in calcium sensitivity. We suggest the mechanism that signals DA contraction also involves tyrosine phosphorylation and the EGFR/p38 /JNK pathway.
Methods and Results: Experiments were performed in DA rings isolated from term pregnancy rabbits. Oxygen-induced DA contraction was significantly inhibited by tyrosine kinase inhibitors (genistein or tyrphostin A23). Orthovanadate, a protein tyrosine phosphatase inhibitor, caused dose-dependent DA contraction and subsequently prevented oxygen-induced DA contraction. Oxygen-induced DA contraction was also by 30 μM AG1478 (EGFR inhibitor, 83%, n=7), 30 μM PP2 (c-Src kinase inhibitor, 72%, n=5), 1 mM AICRA (activator of AMP kinase, 79%, n=4), 30 μM SB203580 (p38 inhibitor, 73%, n=5) and 30 μM of JNK inhibitor II (82%, n= 4), p<0.01 for each. Conversely, 1 μg/mg EGF and 30 μM ansomycin (a p38 and JNK activators, respectively) caused about 50% of the O2-induced contraction, while the AMP kinase inhibitor, compound C, only caused 10% contraction compared to oxygen-induced contraction. 30 μM AG1478 and 30 μM genistein had no effect on KCl-induced contraction. Consistent with the importance of EGFR to O2-constriction, a crucial EGFR tyrosine residue was phosphorylated in 3 human DA smooth muscle cell lines (DASMC) after 3 to 5 minute normoxia. p38, JNK, HSP27 and caldesmon were also phosphorylated in these cells within 5 minutes of normoxia. The oxygen-induced phosphorylation of p38 and JNK is completely reduced by the EGFR inhibitor, AG1478. As observed with oxygen, EGF caused calcium influx and increases cytosolic calcium in human DASMCs.
Conclusions: O2 causes EGFR transactivation and activates the p38 /JNK pathway. This pathway induces calcium influx that contributes to oxygen-induced DA contraction. A clearer understanding of the mechanisms involved in normoxic contraction of the ductus will permit the development of better therapy to close the patent ductus arteriosus.
- © 2010 by American Heart Association, Inc.