Hydrogen Peroxide Regulates Extracellular Superoxide Dismutase Activity and Expression in Neonatal Pulmonary Hypertension

Abstract

We previously demonstrated that superoxide and H 2 O 2 promote pulmonary arterial vasoconstriction in a lamb model of persistent pulmonary hypertension of the newborn (PPHN). Because extracellular superoxide dismutase (ecSOD) augments vasodilation, we hypothesized that H 2 O 2 -mediated ecSOD inactivation contributes to pulmonary arterial vasoconstriction in PPHN lambs. ecSOD activity was decreased in pulmonary arterial smooth muscle cells (PASMCs) isolated from PPHN lambs relative to controls. Exposure to 95% O 2 to mimic hyperoxic ventilation reduced ecSOD activity in control PASMCs. In both cases, these events were associated with increased protein thiol oxidation, as detected by the redox sensor roGFP. Accordingly, exogenous H 2 O 2 decreased ecSOD activity in control PASMCs, and PEG-catalase restored ecSOD activity in PPHN PASMCs. In intact animal studies, ecSOD activity was decreased in fetal PPHN lambs, and in PPHN lambs ventilated with 100% O 2 relative to controls. In ventilated PPHN lambs, administration of a single dose of intratracheal PEGcatalase enhanced ecSOD activity, reduced superoxide levels, and improved oxygenation. We propose that H 2 O 2 generated by PPHN and hyperoxia inactivates ecSOD, and intratracheal catalase enhances enzyme function. The associated decrease in extracellular superoxide augments vasodilation, suggesting that H 2 O 2 scavengers may represent an effective therapy in the clinical management of PPHN. Antioxid. Redox Signal. 15, 1497-1506.

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

“…Interestingly, we previously demonstrated that PPHN is associated with diminished ecSOD activity. 37 We hypothesize that increased expression of ecSOD in steroid-treated FPASMC might reduce oxidant stress in response to hyperoxia, in agreement with studies in rodents that have shown that overexpression of ecSOD attenuates hyperoxic lung injury. 43 One potential consequence of increased oxidative stress is activation of NFκB, a key transcription factor implicated in the pathogenesis of conditions associated with increased ROS, 19,44 including several pulmonary diseases such as primary pulmonary hypertension 45 and the development of chronic lung disease of prematurity.…”

“…16,24,37 Given these differences, we used FPASMC isolated from PPHN lambs as a tool to investigate the aberrant vascular signaling pathways characteristic of PPHN and to determine the effect of hyperoxia on these pathways. Consequently, we investigated the effects of hydrocortisone in PPHN FPASMC to gain mechanistic insights into its beneficial effects on vascular function in intact PPHN lambs.…”

“…30 In this study, we sought to directly determine the effects of hydrocortisone on oxidative stress in isolated PPHN FPASMC. Because we previously reported higher cytosolic protein thiol oxidation in FPASMC from PPHN lambs compared with control animals, 37 we first investigated the effects of hyperoxia and hydrocortisone on cytosolic oxidative stress. After 24-hour exposure of FPASMC to 95% O 2 , cytosolic oxidative stress, as measured by the redox-sensitive probe roGFP, was increased by 1.7 AE 0.3 fold (P < 0.05; Fig.…”

Increased p22phox/Nox4 Expression Is Involved in Remodeling Through Hydrogen Peroxide Signaling in Experimental Persistent Pulmonary Hypertension of the Newborn

“…These newborn lambs display increased PA pressure, pulmonary vascular remodeling, and other physiological changes consistent with clinical PPHN (31,49). Recent evidence suggests that PPHN lambs also exhibit elevated pulmonary vascular oxidant stress and a diminished antioxidant activity relative to control lambs (7,47), which may promote vasoconstriction directly and by impairing the activity of endothelial nitric oxide synthase (eNOS) and downstream cyclic guanozine monophosphate (cGMP) signaling (5,14,37).…”

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

“…Other agents which have shown promising results in laboratory studies by decreasing PVR and promoting vasodilation by various mechanisms include BAY 41-2272 (a novel GC activator), Fasudil (a Rho-kinase inhibitor), intrapulmonary recombinant human VEGF infusion (by upregulating eNOS), and intrapulmonary catalase administration (by decreasing ROS mediated vascular remodelling), high-dose hydrocortisone (by decreasing PDE5 and ROS activity, and increasing cGMP levels, sGC and SOD activity), apocynin (NADPH oxidase inhibitor improve oxygenation by attenuating ROS-mediated vasoconstriction and by increasing NOS activity, increased tetrahydrobiopterin (an eNOS co-factor) levels via sepiapterin supplementation (improves NO production by improving eNOS function and restoring angiogenesis), and antenatal betamethasone (improves response to pulmonary vasodilators by reversing increased superoxide/ decreased cGMP levels and restoring Hsp90-eNOS interactions) [71][72][73][74][75][76][77][78]. Thus, an antioxidant therapeutic approach may have multiple beneficial effects such as increased availability of endogenous and exogenous NO, reduced oxidative stress and reduced lung injury.…”