Blunted hypoxic pulmonary vasoconstriction in experimental neonatal chronic lung disease.
BACKGROUND
Neonatal chronic lung disease (CLD), caused by prolonged mechanical ventilation (MV) with O(2)-rich gas, is the most common cause of long-term hospitalization and recurrent respiratory illness in extremely premature infants. Recurrent episodes of hypoxemia and associated ventilator adjustments often lead to worsening CLD. The mechanism that causes these hypoxemic episodes is unknown. Hypoxic pulmonary vasoconstriction (HPV), which is partially controlled by O(2)-sensitive voltage-gated potassium (K(v)) channels, is an important adaptive response to local hypoxia that helps to match perfusion and ventilation in the lung.


OBJECTIVE
To test the hypothesis that chronic lung injury (CLI) impairs HPV.


METHODS
We studied preterm lambs that had MV with O(2)-rich gas for 3 weeks and newborn rats that breathed 95%-O(2) for 2 weeks, both of which resulted in airspace enlargement and pulmonary vascular changes consistent with CLD.


RESULTS
HPV was attenuated in preterm lambs with CLI after 2 weeks of MV and in newborn rats with CLI after 2 weeks of hyperoxia. HPV and constriction to the K(v)1.x-specific inhibitor, correolide, were preferentially blunted in excised distal pulmonary arteries (dPAs) from hyperoxic rats, whose dPAs exhibited decreased K(v)1.5 and K(v)2.1 mRNA and K(+) current. Intrapulmonary gene transfer of K(v)1.5, encoding the ion channel that is thought to trigger HPV, increased O(2)-sensitive K(+) current in cultured smooth muscle cells from rat dPAs, and restored HPV in hyperoxic rats.


CONCLUSIONS
Reduced expression/activity of O(2)-sensitive K(v) channels in dPAs contributes to blunted HPV observed in neonatal CLD.
Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada.
Gloria Juliana
GJ
Rey-Parra
Stephen L
SL
Archer
Richard D
RD
Bland
Kurt H
KH
Albertine
David P
DP
Carlton
Soo-Chul
SC
Cho
Beth
B
Kirby
Al
A
Haromy
Farah
F
Eaton
Xichen
X
Wu
Bernard
B
Thébaud
D000818:Animals; D000831:Animals, Newborn; D001997:Bronchopulmonary Dysplasia / Q000503:physiopathology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D015870:Gene Expression / Q000235:genetics; D018014:Gene Transfer Techniques; D005865:Gestational Age; D006706:Homeostasis; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007231:Infant, Newborn; D008168:Lung / Q000098:blood supply*; D032389:Myocytes, Smooth Muscle / Q000502:physiology; D010100:Oxygen / Q000502:physiology*; D010102:Oxygen Inhalation Therapy; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012756:Sheep; D014661:Vasoconstriction / Q000502:physiology*; D014692:Ventilation-Perfusion Ratio / Q000502:physiology
D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D010100:Oxygen