SOD and inhaled nitric oxide normalize phosphodiesterase 5 expression and activity in neonatal lambs with persistent pulmonary hypertension

Abstract

Phosphodiesterase 5 (PDE5) and soluble guanylate cyclase (sGC) are key regulators of cGMP and pulmonary vascular tone. We sought to determine the impact of mechanical ventilation with O(2) with or without inhaled nitric oxide (iNO) or recombinant human Cu/Zn SOD (rhSOD) on sGC, PDE5, and cGMP in the ovine ductal ligation model of persistent pulmonary hypertension of the newborn (PPHN). PPHN lambs were ventilated with 100% O(2) for 24 h alone or combined with either inhalation of 20 parts per million (ppm) iNO continuously or a single intratracheal dose of rhSOD (5 mg/kg). Ventilated PPHN lambs were compared with PPHN fetuses, control fetuses, and 1-day-old spontaneously breathing lambs (1DSB). In the small pulmonary arteries of 1DSB lambs, sGC expression increased, PDE5 expression decreased, and cGMP concentrations increased relative to fetal levels. In PPHN lambs ventilated with 100% O(2), sGC activity increased to levels comparable with 1DSB levels. However, PDE5 expression and activity increased, and cGMP levels remained at fetal levels. Addition of either iNO or rhSOD decreased PDE5 expression and activity in PPHN lambs and increased cGMP levels to levels comparable with 1DSB lambs. These data suggest that ventilation of PPHN lambs with 100% O(2) impairs cGMP-mediated vasodilation in part due to increased PDE5 expression and activity. The addition of either iNO or rhSOD normalized PDE5 and cGMP levels. Thus therapies designed to decrease PDE5 and increase cGMP, such as iNO and rhSOD, may prove useful in the treatment of PPHN in newborn infants.

Hydrocortisone Normalizes Phosphodiesterase‐5 Activity in Pulmonary Artery Smooth Muscle Cells from Lambs with Persistent Pulmonary Hypertension of the Newborn

“…30 We previously reported that PDE5 activity is upregulated by increased ROS and that this effect is reversed by treatment with antioxidants in intact neonatal PPHN lambs and in smooth muscle cells isolated from them. 13,14,16 Therefore, we next investigated the effects of hyperoxia with and without hydrocortisone on oxidative stress in two subcellular compartments, using a previously characterized redox-sensitive probe, roGFP. As might be expected, exposure of PPHN FPASMC to hyperoxia for 24 hours resulted in increased oxidative stress, both in the cytosol and in the mitochondrial matrix (Fig.…”

“…13 Moreover, PPHN may independently alter expression and activity of key enzymes in the NO-cGMP pathway. For example, ventilation with 100% oxygen increases PDE5 activity in PAs of PPHN lambs more than in control lambs, 13,14 and basal PDE5 activity is higher in FPASMC isolated from PPHN relative to healthy lambs. 16 Hyperoxia produces lung injury in part through increased formation of reactive oxygen species (ROS).…”

“…cGMP is in turn inactivated by the cGMP-specific phosphodiesterase, or phosphodiesterase-5 (PDE5), the predominant phosphodiesterase in lung vasculature and an important therapeutic target in PPHN. 12 Although high concentrations of oxygen are widely used to promote pulmonary vasodilation in infants with PPHN, new evidence indicates that such therapy may upregulate PDE5 13,14 and paradoxically increase pulmonary vascular contractility. 15 We previously demonstrated that ventilation of healthy neonatal sheep with 100% O 2 for 24 hours increases PDE5 protein expression and activity in the resistance pulmonary arteries (PAs).…”

Endothelial and Smooth Muscle Cell Interactions in the Pathobiology of Pulmonary Hypertension

“…A dysfunctional EDNOsGC-cGMP-PKG signaling pathway constitutes one of the most fundamental and initial changes in the development of PH (1,33), resulting from aberrant expression of eNOS (34), reduced NO production caused by eNOS uncoupling (35)(36)(37)(38), diminished NO bioavailability caused by oxidative stress (39,40), diminished activities of sGC (41,42) and PKG (26,(43)(44)(45)(46), and augmented activity of phosphodiesterase type 5 (47).…”

Persistent Pulmonary Hypertension of the Newborn: Recent Advances in the Management

“…Studies have demonstrated that recombinant human SOD (rhSOD) augments PDE-5 expression, vasodilatory response to iNO and oxygenation in PPHN lamb models [69,70]. Furthermore, rhSOD treatment appeared to block formation of oxidants like peroxynitrite and isoprostanes.…”