COX-1-derived PGE2 and PGE2 type 1 receptors are vital for angiotensin II- induced formation of reactive oxygen species and Ca2+ influx in the subfornical organ

Regulation of blood pressure by angiotensin II (ANG II) is a process that involves the reactive oxygen species (ROS) and calcium. We have shown that ANG-II type 1 receptor (AT(1)R) and prostaglandin E-2 (PGE(2)) type 1 receptors (EP1R) are required in the subfornical organ (SFO) for ROS-mediated hypertension induced by slow-pressor ANG-II infusion. However, the signaling pathway associated with this process remains unclear. We sought to determine mechanisms underlying the ANG II-induced ROS and calcium influx in mouse SFO cells. Ultrastructural studies showed that cyclooxygenase 1 (COX-1) codistributes with AT(1)R in the SFO, indicating spatial proximity. Functional studies using SFO cells revealed that ANG II potentiated PGE(2) release, an effect dependent on AT(1)R, phospholipase A(2) (PLA(2)) and COX-1. Furthermore, both ANG II and PGE(2) increased ROS formation. While the increase in ROS initiated by ANG II, but not PGE(2), required the activation of the AT(1)R/PLA(2)/COX-1 pathway, both ANG II and PGE(2) were dependent on EP1R and Nox2 as downstream effectors. Finally, ANG II potentiated voltage-gated L-type Ca2+ currents in SFO neurons via the same signaling pathway required for PGE(2) production. Blockade of EP1R and Nox2-derived ROS inhibited ANG II and PGE(2)-mediated Ca2+ currents. We propose a mechanism whereby ANG II increases COX-1-derived PGE(2) through the AT(1)R/PLA(2) pathway, which promotes ROS production by EP1R/Nox2 signaling in the SFO. ANG II-induced ROS are coupled with Ca2+ influx in SFO neurons, which may influence SFO-mediated sympathoexcitation. Our findings provide the first evidence of a spatial and functional framework that underlies ANG-II signaling in the SFO and reveal novel targets for antihypertensive therapies.