Hydrocortisone normalizes oxygenation and cGMP regulation in lambs with persistent pulmonary hypertension of the newborn

Abstract

In the pulmonary vasculature, cGMP levels are regulated by soluble guanylate cyclase (sGC) and phosphodiesterase 5 (PDE5). We previously reported that lambs with persistent pulmonary hypertension of the newborn (PPHN) demonstrate increased reactive oxygen species (ROS) and altered sGC and PDE5 activity, with resultant decreased cGMP. The objective of this study was to evaluate the effects of hydrocortisone on pulmonary vascular function, ROS, and cGMP in the ovine ductal ligation model of PPHN. PPHN lambs were ventilated with 100% O(2) for 24 h. Six lambs received 5 mg/kg hydrocortisone every 8 h times three doses (PPHN-hiHC), five lambs received 3 mg/kg hydrocortisone followed by 1 mg·kg(-1)·dose(-1) times two doses (PPHN-loHC), and six lambs were ventilated with O(2) alone (PPHN). All groups were compared with healthy 1-day spontaneously breathing lambs (1DSB). O(2) ventilation of PPHN lambs decreased sGC activity, increased PDE5 activity, and increased ROS vs. 1DSB lambs. Both hydrocortisone doses significantly improved arterial-to-alveolar ratios relative to PPHN lambs, decreased PDE5 activity, and increased cGMP relative to PPHN lambs. High-dose hydrocortisone also increased sGC activity, decreased PDE5 expression, decreased ROS, and increased total vascular SOD activity vs. PPHN lambs. These data suggest that hydrocortisone treatment in clinically relevant doses improves oxygenation and decreases hyperoxia-induced changes in sGC and PDE5 activity, increasing cGMP levels. Hydrocortisone reduces ROS levels in part by increasing SOD activity in PPHN lambs ventilated with 100% O(2.) We speculate that hydrocortisone increases cGMP by direct effects on sGC and PDE5 expression and by attenuating abnormalities induced by oxidant stress.

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

“…3). We recently reported that hydrocortisone decreases vascular oxidative stress in ventilated lambs with PPHN, 30 and in this study, we now report that hydrocortisone treatment selectively decreases cytosolic oxidative stress in pulmonary vascular smooth muscle without affecting mitochondrial matrix ROS (Fig. 3).…”

“…This is similar to our recent findings that hydrocortisone normalizes PDE5 activity in resistance PAs of PPHN lambs ventilated with 100% O 2 for 24 hours. 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.…”

“…25 We recently demonstrated improved oxygenation and decreased PDE5 activity in PPHN lambs treated with hydrocortisone. 30 Given the wide variety of potential effects of steroids, it is not yet clear what specific mechanisms are responsible for the effects of hydrocortisone on PDE5. We recently reported that NFκB activity is elevated in fetal lambs with pulmonary hypertension.…”

“…30 In this study, we determined the effects of hydrocortisone treatment on PDE5 in hyperoxia-exposed FPASMC isolated from PPHN lambs. Similar to our recent report, 16 24 hours of hyperoxia did not significantly alter PDE5 protein expression in PPHN FPASMC (Fig.…”

“…13 Hydrocortisone treatment of intact ventilated PPHN lambs decreased markers of oxidative stress and decreased PDE5 activity relative to untreated animals. 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.…”