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Impaired nitric oxide-cGMP signaling contributes to severe pulmonary hypertension after birth, which may in part be due to decreased soluble gnanylate cyclase (sGC) activity. Cinacignat (BAY 58-2667) is a novel sGC activator that causes vasodilation, even in the presence of oxidized heine or heine-free sGC, but its hemodynamic effects have not been studied in the perinatal lung. We performed surgery on eight fetal (126 [+ or -] 2 days gestation) lambs (full term = 147 days) and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic flow transducer was placed on the left pulmonary artery to measure blood flow, and a catheter was placed in the left pulmonary artery for drug infusion. Cinaciguat (0.1-100 [micro]g over 10 rain) caused dose-related increases in pulmonary blood flow greater than fourfold above baseline and reduced pulmonary vascular resistance by 80%. Treatment with IH-[l,2,4]oxadiazolo[4,3-a]quinoxalin-l-one (ODQ), an sGC-oxidizing inhibitor, enhanced cinacignat-induced pulmonary vasodilation by > 120%. The pulmonary vasodilator effect of cinacignat was prolonged, decreasing pulmonary vascular resistance for > 1.5 h after brief infusion. In vitro stimulation of ovine fetal pulmonary artery smooth muscle cells with cinacignat after ODQ treatment resulted in a 14-fold increase in cGMP compared with non-ODQ-treated cells. We conclude that cinaciguat causes potent and sustained fetal pulmonary vasodilation that is augmented in the presence of oxidized sGC and speculate that cinacignat may have therapeutic potential for severe neonatal pulmonary hypertension. BAY 58-2667; cGMP; nitric oxide; persistent pulmonary hypertension of the newborn; pulmonary hypertension

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by endothelial dysfunction and decreased vascular growth. The role of Rho kinase activity in modulating endothelial function and regulating angiogenesis during normal lung development and in PPHN is unknown. We hypothesized that PPHN increases Rho kinase activity in fetal pulmonary artery endothelial cells (PAECs) and impairs angiogenesis in vitro. Proximal PAECs were harvested from fetal sheep with partial ligation of the ductus arteriosus in utero (PPHN) and age-matched controls. Rho kinase activity was measured by RhoA, Rho GTP, and phosphorylated MYPT-1 protein content. The effects of Rho kinase activity on angiogenesis, endothelial nitric oxide (NO) synthase (eNOS) protein expression, and NO production were determined in normal and PPHN PAECs. Angiogenesis was assessed by tube formation in vitro with/without Y-27632 (a Rho kinase inhibitor) and calpeptin (a Rho kinase activator) in the presence/absence of N-nitro-L-arginine (L-NA, an NOS inhibitor). RhoA, Rho GTP, and phosphorylated MYPT-1 protein were increased in PPHN PAECs. Tube formation was reduced 29% in PPHN PAECs (P < 0.001) and increased with Y-27632 treatment in normal and PPHN PAECs, with PPHN PAECs achieving levels similar to those of normal PAECs. L-NA inhibited the Y-27632-induced increase in tube formation in normal, but not PPHN, PAECs. Calpeptin reduced tube formation in normal and PPHN PAECs. eNOS expression was reduced 42% in PPHN PAECs (P < 0.01). Y-27632 increased eNOS protein and NO production in normal and PPHN PAECs. Calpeptin decreased eNOS protein only in normal PAECs but reduced NO production in normal and PPHN PAECs. We conclude that Rho kinase activity is increased in PPHN PAECs and impairs angiogenesis and downregulates eNOS protein and NO production in vitro. persistent pulmonary hypertension of the newborn; vasculogenesis; nitric oxide; endothelial nitric oxide synthase; lung vascular development

Recent studies suggest that VEGF may worsen pulmonary edema during acute lung injury (ALI), but, paradoxically, impaired VEGF signaling contributes to decreased lung growth during recovery from ALI due to neonatal hyperoxia. To examine the diverse roles of VEGF in the pathogenesis of and recovery from hyperoxia-induced ALI, we hypothesized that exogenous recombinant human VEGF (rhVEGF) treatment during early neonatal hyperoxic lung injury may increase pulmonary edema but would improve late lung structure during recovery. Sprague-Dawley rat pups were placed in a hyperoxia chamber (inspired [O.sub.2] fraction 0.9) for postnatal days 2-14. Pups were randomized to daily intramuscular injections of [rhVEGF.sub.165] (20 [micro]g/kg) or saline (controls). On postnatal day 14, rats were placed in room air for a 7-day recovery period. At postnatal days 3, 14, and 21, rats were killed for studies, which included body weight and wet-to-dry lung weight ratio, morphometric analysis ]including radial alveolar counts (RAC), mean linear intercepts (MLI), and vessel density], and lung endothelial NO synthase (eNOS) protein content by Western blot analysis. Compared with room air controls, hyperoxia increased pulmonary edema by histology and wet-to-dry lung weight ratios at postnatal day 3, which resolved by day 14. Although treatment with rhVEGF did not increase edema in control rats, rhVEGF increased wet-to-dry weight ratios in hyperoxia-exposed rats at postnatal days 3 and 14 (P < 0.01). Compared with room air controls, hyperoxia decreased RAC and increased MLI at postnatal days 14 and 21. Treatment with VEGF resulted in increased RAC by 181% and decreased MLI by 55% on postnatal day 14 in the hyperoxia group (P < 0.01). On postnatal day 21, RAC was increased by 176% and MLI was decreased by 58% in the hyperoxia group treated with VEGF. rhVEGF treatment during hyperoxia increased eNOS protein on postnatal day 3 by threefold (P < 0.05). We conclude that rhVEGF treatment during hyperoxia-induced ALI transiently increases pulmonary edema but improves lung structure during late recovery. We speculate that VEGF has diverse roles in hyperoxia-induced neonatal lung injury, contributing to lung edema during the acute stage of ALI but promoting repair of the lung during recovery. bronchopulmonary dysplasia; lung development; vascular endothelial growth factor; alveolarization; angiogenesis

The original version of this article unfortunately contained a mistake. The collaborators of the Neonatal Kidney Collaborative (NKC) were not named individually. The list of all collaborators is given below., Author(s): Megan J. Kirkley [sup.1] [sup.2] , Louis Boohaker [sup.3] , Russell Griffin [sup.4] , Danielle E. Soranno [sup.5] , Jason Gien [sup.1] , David Askenazi [sup.6] , Katja M. [...]