Impact of early life AT1 blockade on adult cardiac morpho-functional changes and the renin-angiotensin system in a model of neonatal high oxygen-induced cardiomyopathy

We previously reported that neonatal blockade of angiotensin II AT1 receptor prevents cardiac changes in 4 weeks rats with neonatal hyperoxia-induced cardiomyopathy, a recognized model of prematurity-related deleterious conditions. Considering the importance of AT1 receptor and the renin angiotensin system (RAS) in normal development, the present study aimed to investigate the adult effects of neonatal AT1 blockade on left ventricle (LV) in rats exposed to neonatal hyperoxia. Sprague-Dawley pups were exposed to 80% O2 or room air from days 3–10. AT1 blocker (losartan) or H2O were given by gavage from day 8–10. LV function (echo and intraventricular pressure), histology and expression of RAS components were examined in 15–16 weeks old adult males. Losartan treatment prevented myocardial fibrosis, LV wall thickening and stroke volume reduction in rats exposed to high O2 in the neonatal period. However, Losartan treatment of O2-exposed pups led to reduced ejection fraction (EF) and fractional shortening (FS), and did not prevent changes in diastolic function. Losartan also did not prevent increased LV AT2 and decreased angiotensin-(1–7) Mas receptors expression observed in high O2-exposed rats. Neonatal Losartan attenuated long-term impact of neonatal hyperoxia but also led to decreased EF and FS. Increased AT2 and decreased Mas receptor expression observed in O2-exposed group were unaffected by Losartan treatment. Our results show that early life Losartan treatment aimed at preventing cardiac consequences of neonatal deleterious conditions may also comprise detrimental effects that require further investigation prior to clinical translation in developing children.