The pathophysiology underlying neonatal pulmonary hypertension has received relatively little study compared to adult models, even though it may involve different mechanisms. Thus, the long-term goal is to improve the understanding of the pathogenesis of neonatal pulmonary hypertension so that more effective therapies can be developed. Almost all of the research regarding neonatal pulmonary hypertension has been directed at devising therapies to acutely decrease pulmonary vascular resistance. Therapies for preventing the onset or progression of neonatal pulmonary hypertension have received little attention and have largely involved manipulating the nitric oxide (NO) pathway. Yet, not all infants respond favorably to inhaled NO. Our preliminary data demonstrate that rather than a singular effect attributable to NO, derangements in the prostanoid system, which include prostacyclin (PGI2) and thromboxane (TXA2), are key to the pathogenesis of hypoxia-induced neonatal pulmonary hypertension. Our overall hypothesis is that distinct disruptions of the prostanoid signaling pathway occur with sustained hypoxia in endothelial cells and smooth muscle cells of small pulmonary arteries (SPA) and lead to inappropriate constriction of pulmonary resistance vessels and the development of pulmonary hypertension. At the core of our methodology is the use of SPA as they are the vascular site most relevant to the development of pulmonary hypertension. This proposal will investigate the following specific hypotheses: (a) the cyclooxygenase (COX) 1-PGI2 axis is disrupted in endothelial cells of SPA with sustained hypoxemia leading to decreased dilator prostanoid production; (b) the COX 2-TXA2 axis is enhanced in smooth muscle cells of SPA with sustained hypoxia so that the ratio of constrictor to dilator prostanoid production is increased; (c) the change in ratio of constrictor to dilator prostanoid production alters smooth muscle cell K+ conductance and membrane potential leading to inappropriate constriction and pulmonary hypertension.
Specific Aim 1 will (a) determine the amounts, cellular sources and relative contributions of COX 1 and COX 2 biosynthetic pathways to PGI2 and TXA2 production using enzyme immunoassay (EIA) and cannulated artery techniques; (b) evaluate the effect of PGI2 and TXA2 on SPA tone (cannulated artery technique); (c) establish the predominant cellular localization of the major prostanoid enzymes (immunostaining technique) and (d) determine the role of various K+ channels in mediating vascular responses to PGI2 (microelectrode technique).
Specific Aim 2 will (a) determine whether the amounts and/or predominant cellular sources of production of PGI2 and TXA2 are altered in SPA from piglets exposed to chronic hypoxia (EIA and cannulated artery techniques); (b) evaluate whether the sensitivity to PGI2 and TXA2 has been altered by chronic hypoxia (cannulated artery technique); (c) determine whether mRNA levels for the major enzymes (RNase protection assay), protein abundance of the major enzymes (immunoblot technique) or the cellular localization of the major enzymes (immunostaining) underlying PGI2 and TXA2 production are affected by chronic hypoxia; (d) evaluate whether the effect from K+ channels in mediating dilation and constriction from PGI2 and TXA2 is involved with the development of pulmonary hypertension (microelectrode technique). These studies should provide important information for improving treatment of infants with pulmonary hypertension.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL068572-03
Application #
6686400
Study Section
Human Embryology and Development Subcommittee 1 (HED)
Program Officer
Berberich, Mary Anne
Project Start
2001-12-01
Project End
2005-11-30
Budget Start
2003-12-01
Budget End
2005-11-30
Support Year
3
Fiscal Year
2004
Total Cost
$252,000
Indirect Cost
Name
Wake Forest University Health Sciences
Department
Pediatrics
Type
Schools of Medicine
DUNS #
937727907
City
Winston-Salem
State
NC
Country
United States
Zip Code
27157
Fike, Candice D; Aschner, Judy L; Kaplowitz, Mark R et al. (2013) Reactive oxygen species scavengers improve voltage-gated K(+) channel function in pulmonary arteries of newborn pigs with progressive hypoxia-induced pulmonary hypertension. Pulm Circ 3:551-63
Fike, Candice D; Dikalova, Anna; Slaughter, James C et al. (2013) Reactive oxygen species-reducing strategies improve pulmonary arterial responses to nitric oxide in piglets with chronic hypoxia-induced pulmonary hypertension. Antioxid Redox Signal 18:1727-38
Fike, Candice D; Aschner, Judy L (2013) Looking beyond PPHN: the unmet challenge of chronic progressive pulmonary hypertension in the newborn. Pulm Circ 3:454-66
Fike, Candice D; Aschner, Judy L (2013) Spread the word, children are still not ""small adults"". Pulm Circ 3:3-4
Fike, Candice D; Kaplowitz, Mark; Zhang, Yongmei et al. (2012) Effect of a phosphodiesterase 5 inhibitor on pulmonary and cerebral arteries of newborn piglets with chronic hypoxia-induced pulmonary hypertension. Neonatology 101:28-39
Fike, Candice D; Sidoryk-Wegrzynowicz, Marta; Aschner, Michael et al. (2012) Prolonged hypoxia augments L-citrulline transport by system A in the newborn piglet pulmonary circulation. Cardiovasc Res 95:375-84
Fike, Candice D; Aschner, Judy L; Slaughter, James C et al. (2011) Pulmonary arterial responses to reactive oxygen species are altered in newborn piglets with chronic hypoxia-induced pulmonary hypertension. Pediatr Res 70:136-41
Fike, Candice D; Pfister, Sandra L; Slaughter, James C et al. (2010) Protein complex formation with heat shock protein 90 in chronic hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Heart Circ Physiol 299:H1190-204
Aschner, Judy L; Zeng, Heng; Kaplowitz, Mark R et al. (2009) Heat shock protein 90-eNOS interactions mature with postnatal age in the pulmonary circulation of the piglet. Am J Physiol Lung Cell Mol Physiol 296:L555-64
Dennis, Kathleen E; Aschner, J L; Milatovic, D et al. (2009) NADPH oxidases and reactive oxygen species at different stages of chronic hypoxia-induced pulmonary hypertension in newborn piglets. Am J Physiol Lung Cell Mol Physiol 297:L596-607

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