Hyperoxia exposure is an important factor involved in the pathogenesis of bronchopulmonary dysplasia (BPD). BPD is a major long-term morbidity in premature infants, which imposes long-term medical and societal burden for the affected infants. Impaired lung vascular and alveolar growth is a characteristic feature of BPD histology. Recent studies demonstrated that poor blood vessel growth in the lungs may be the critical factor involved in the development of BPD. Blood vessel growth is controlled by several angiogenic growth factors and nitric oxide (NO) released by endothelial NO synthase (eNOS), appears to be the key mediator for angiogenic growth factors. Adequate eNOS function relies on several co-factors, including tetrahydrobiopterin (BH4). BH4 is formed by either de novo pathway or by salvage pathway. GTP-chclohydrolase-1 (GCH1) is the rate-limiting enzyme of intracellular BH4 synthesis. Decreased intracellular BH4 levels, or oxidation of BH4 to BH2, uncouple eNOS activity with more reactive oxygen species (ROS) forming in the endothelial cells instead of NO. Decreased NO formation can increase pulmonary artery vasomotor tone and aggravate respiratory distress in premature infants. Premature infants with respiratory distress often require the use of oxygen and mechanical ventilation;both of which increase ROS formation in premature lungs. Pulmonary artery endothelial cells from premature lambs have decreased BH4 levels and GCH1 expression, and eNOS uncoupling after exposure to hyperoxia, whereas, sepiapterin partially corrects these changes. We hypothesize that increasing endogenous BH4 in the lung can protect premature lungs from hyperoxic injury. We plan to investigate our hypothesis in Sprague-Dawley rat pups exposed to hyperoxia during the first 10 days of postnatal life. Studies under specific aim 1 will investigate BH4 levels and the expression of BH4 forming enzymes in their lungs during hyperoxia. Expression of GCH1 will be studied at transcriptional, translational, and post-translational levels by chromatin immunoprecipitation, DNA methylation, quantitative real-time polymerase chain reaction, and immunoblotting. Studies under specific aim 2 will investigate the mechanistic link between BH4 depletion and hyperoxia-induced impairment of lung growth. These studies will be done by supplementing rat pups with sepiapterin during hyperoxia exposure, to increase BH4 levels. Lung histology and pulmonary artery reactivity will be used to investigate the protective effect of increasing endogenous BH4 levels. This pilot study will provide information on the potential use of sepiapterin, a BH4 analogue, in preventing or treating BPD.

Public Health Relevance

The project is to use Sprague-Dawley newborn rat pups to study the role of tetrahydrobiopterin (BH4) in hyperoxic lung injury in newborn. Protein expression, mRNA, and epigenetic control of BH4 forming enzymes in newborn lungs will be explored. Role of BH4 in lung growth will also be studied by supplementing endogenous BH4 via sepiapterin.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Small Research Grants (R03)
Project #
1R03HD073274-01
Application #
8353353
Study Section
Pediatrics Subcommittee (CHHD)
Program Officer
Raju, Tonse N
Project Start
2012-08-01
Project End
2014-07-31
Budget Start
2012-08-01
Budget End
2013-07-31
Support Year
1
Fiscal Year
2012
Total Cost
$76,500
Indirect Cost
$26,500
Name
Medical College of Wisconsin
Department
Pediatrics
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
Jing, Xigang; Huang, Yi-Wen; Jarzembowski, Jason et al. (2017) Caffeine ameliorates hyperoxia-induced lung injury by protecting GCH1 function in neonatal rat pups. Pediatr Res 82:483-489
Tadokoro, Kent S; Rana, Ujala; Jing, Xigang et al. (2016) Nogo-B Receptor Modulates Pulmonary Artery Smooth Muscle Cell Function in Developing Lungs. Am J Respir Cell Mol Biol 54:892-900
Hu, Wenquan; Zhang, Wenwen; Chen, Yuanli et al. (2016) Nogo-B receptor deficiency increases liver X receptor alpha nuclear translocation and hepatic lipogenesis through an adenosine monophosphate-activated protein kinase alpha-dependent pathway. Hepatology 64:1559-1576
Teng, Ru-Jeng; Wu, Tzong-Jin; Afolayan, Adeleye J et al. (2016) Nitrotyrosine impairs mitochondrial function in fetal lamb pulmonary artery endothelial cells. Am J Physiol Cell Physiol 310:C80-8
Mahajan, Chaitali N; Afolayan, Adeleye J; Eis, Annie et al. (2015) Altered prostanoid metabolism contributes to impaired angiogenesis in persistent pulmonary hypertension in a fetal lamb model. Pediatr Res 77:455-62
Afolayan, Adeleye J; Teng, Ru-Jeng; Eis, Annie et al. (2014) Inducible HSP70 regulates superoxide dismutase-2 and mitochondrial oxidative stress in the endothelial cells from developing lungs. Am J Physiol Lung Cell Mol Physiol 306:L351-60
Cohen, Susan S; Powers, Bethany R; Lerch-Gaggl, Alexandra et al. (2014) Impaired cerebral angiogenesis in the fetal lamb model of persistent pulmonary hypertension. Int J Dev Neurosci 38:113-8
Teng, Ru-Jeng; Rana, Ujala; Afolayan, Adeleye J et al. (2014) Nogo-B receptor modulates angiogenesis response of pulmonary artery endothelial cells through eNOS coupling. Am J Respir Cell Mol Biol 51:169-77
Teng, Ru-Jeng; Wu, Tzong-Jin (2013) Persistent pulmonary hypertension of the newborn. J Formos Med Assoc 112:177-84
Teng, Ru-Jeng; Du, Jianhai; Afolayan, Adeleye J et al. (2013) AMP kinase activation improves angiogenesis in pulmonary artery endothelial cells with in utero pulmonary hypertension. Am J Physiol Lung Cell Mol Physiol 304:L29-42