Hypoxia-inducible factors HIF-1alpha and HIF-2alpha are decreased in an experimental model of severe respiratory distress syndrome in preterm lambs.
Respiratory distress syndrome (RDS) secondary to preterm birth and surfactant deficiency is characterized by severe hypoxemia, lung injury, and impaired production of nitric oxide (NO) and vascular endothelial growth factor (VEGF). Since hypoxia-inducible factors (HIFs) mediate the effects of both NO and VEGF in part through regulation by prolyl-hydroxylase-containing domains (PHDs) in the presence of oxygen, we hypothesized that HIF-1alpha and -2alpha in the lung are decreased following severe RDS in preterm neonatal lambs. To test this hypothesis, fetal lambs were delivered at preterm gestation (115-day gestation, term = 145 days; n = 4) and mechanically ventilated for 4 h. Lambs developed respiratory failure characterized by severe hypoxemia despite treatment with mechanical ventilation with high inspired oxygen concentrations. Lung samples were compared with nonventilated control animals at preterm (115-day gestation; n = 3) and term gestation (142-day gestation; n = 3). We found that HIF-1alpha protein expression decreased (P < 0.05) and PHD-2 expression increased (P < 0.005) at birth in normal term animals before air breathing. Compared with age-matched controls, HIF-1alpha protein and HIF-2alpha protein expression decreased by 80% and 55%, respectively (P < 0.005 for each) in preterm lambs with RDS. Furthermore, VEGF mRNA was decreased by 40%, and PHD-2 protein expression doubled in RDS lambs. We conclude that pulmonary expression of HIF-1alpha, HIF-2alpha, and the downstream target of their regulation, VEGF mRNA, is impaired following RDS in neonatal lambs. We speculate that early disruption of HIF and VEGF expression after preterm birth and RDS may contribute to long-term abnormalities in lung growth, leading to bronchopulmonary dysplasia.
Grover
Theresa R
TR
University of Colorado School of Medicine, Pediatric Heart Lung Center, Department of Pediatrics, and National Jewish Medical and Research Center, Denver, Colorado, USA. grover.theresa@tchden.org
Asikainen
Tiina M
TM
Kinsella
John P
JP
Abman
Steven H
SH
White
Carl W
CW
D000818:Animals; D000831:Animals, Newborn; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005865:Gestational Age; D018398:Homeodomain Proteins / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D017874:Immediate-Early Proteins / Q000378:metabolism; D008168:Lung / Q000196:embryology / Q000503:physiopathology; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D011247:Pregnancy; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000378:metabolism* / Q000503:physiopathology* / Q000628:therapy; D012720:Severity of Illness Index; D012756:Sheep; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017874:Immediate-Early Proteins; D052250:Nitric Oxide Synthase Type III; D011393:Procollagen-Proline Dioxygenase; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1