Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB089

Poster Communications

Cinaciguat (BAY-582667) as activator of the soluble guanylyl cyclase (sGC) in chronically hypoxic and pulmonary hypertensive neonatal lambs

F. A. Beñaldo3, C. Araya-Quijada3, G. Ebensperger3, C. P. Guzmán-Silva3, S. Castillo-Galan3, M. Serón-Ferré3, E. A. Herrera3,1, R. V. Reyes3,1, F. Moraga2, A. J. Llanos3,1

1. International Center for Andean Studies (INCAS), Universidad de Chile, Santiago, Chile. 2. Facultad de Medicina, Universidad Católica del Norte, Coquimbo, Chile. 3. Programa de Fisiopatologia, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.

Chronically hypoxic and pulmonary hypertensive neonatal lambs at high altitude have an increased NO production and a decreased sGC protein expression in the lung, relative to low altitude normotensive lambs. Here, we proposed that sGC enzymatic function is reduced due to an oxidized enzyme at low tissue concentration, the former triggered by an elevated ROS production by hypoxia. We administered cinaciguat, a drug that is able to activate oxidized sGC, augmenting its function in newborn sheep gestated and born and at high altitude. Twelve newborn sheep, born and raised at Putre Research Station, INCAS (3,600 m), were catheterized under general anaesthesia with ketamine (10 mg/kg im), xylacine (0.1-0.5 mg/kg im) and atropine (0.04 mg/kg im), with additional local infiltration of 2% lidocaine, in pulmonary artery (Swan Ganz catheter), abdominal aorta and vena cava at 3-4 days old. After surgery, oxitetraciclin (20 mg/kg sc) and sodium metamizole (0.1 mg/kg im) were given immediately postoperatively for 3 days. The neonates were separated into two groups: 6 controls and 6 cinaciguat-treated lambs. The treated neonates received a daily infusion of cinaciguat (35 µg/kg) into the pulmonary circulation during 7 days. At day 8, the animals were subjected to an acute episode of superimposed hypoxia, that consider 30min breathing air, 30min of hypoxemia (PO2: 32±1 mmHg) and 30min of recovery. We determined daily and during the episode of superimposed hypoxia, pulmonary arterial pressure (mPAP), heart rate, cardiac output and pulmonary vascular resistance (PVR). At 15 days old, the lambs were euthanized, heart chambers were dissected, weighed and pulmonary samples were collected for molecular biology (phosphorylated protein 38/total protein 38; pp38/p38 ratio) WB; histology (muscle layer in small pulmonary arteries) and immunohistochemistry (Ki67) studies. All procedures were approved by the Local Bioethical Committee (CBA0643 FMUCH). Cinaciguat did not change the mPAP, but did change the PVR in the last day of treatment (p<0.05). Cinaciguat induced a decrease response in mPAP during the episode of acute hypoxia (p<0.05) relative to controls lambs. The treatment reduced the RV/LV + Septum ratio (p<0.05), decreased the muscle layer in small pulmonary arteries (p<0.05), showing diminished cardiopulmonary remodelling than control lambs. However, the lung ratio of pp38/p38 and positive Ki67 (proliferative markers) were similar between groups. We conclude that cinaciguat was able to decreased pulmonary artery responsiveness in the last day of treatment and in acute hypoxia in pulmonary hypertensive neonatal lambs. This was associated with a marked decrease in pathologic cardiopulmonary remodelling, presumable due to an increase in apoptosis and/or autophagy in the pulmonary arteries. FONDECYT 1140647, 1120605, 1130424 & 1151119.

Where applicable, experiments conform with Society ethical requirements