Platelet-activating factor stimulates ovine foetal pulmonary vascular smooth muscle cell proliferation: role of nuclear factor-kappa B and cyclin-dependent kinases.
OBJECTIVE
Platelet-activating factor (PAF) is implicated in pathogenesis of persistent pulmonary hypertension of the neonate (PPHN); PAF is a mitogen for lung fibroblasts. PAF's role in pulmonary vascular smooth muscle cell (PVSMC) proliferation and in hypoxia-induced pulmonary vein (PV) remodelling has not been established and mechanisms for PAF's cell-proliferative effects are not well understood. We investigated involvement of PAF and PAF receptors in PVSMC proliferation.


METHODS
Cells from pulmonary arteries (SMC-PA) and veins (SMC-PV) were serum starved for 72 h in 5% CO2 in air (normoxia). They were cultured for 24 h more in normoxia or 2% O(2) (hypoxia) in 0.1% or 10% foetal bovine serum with 5 microCi/well of [(3)H]-thymidine, with and without 10 nm PAF. Nuclear factor-kappa B (NF-kappaB), CDK2 and CDK4 protein expression, and their roles in cell proliferation control were studied.


RESULTS
PAF and hypoxia increased SMC-PA and SMC-PV proliferation. WEB2170 inhibited PAF-induced cell proliferation while lyso-PAF had no effect. SMC-PV proliferated more than SMC-PA and PAF plus hypoxia augmented NF-kappaB protein expression. NF-kappaB inhibitory peptide attenuated PAF-induced cell proliferation by 50% and PAF increased CDK2 and CDK4 protein expression. The data show that hypoxia and PAF up-regulate PVSMC proliferation via PAF receptor-specific pathway involving NF-kappaB, CDK2 and CDK4 activations.


CONCLUSIONS
They suggest that in vivo, in foetal lung low-oxygen environment, where PAF level is high, proliferation of PVSMC will occur readily to modulate PV development and that failure of down-regulation of PAF effects postnatally may result in PPHN.
Ibe
B O
BO
Division of Neonatology, Harbor-UCLA Medical Center, Los Angeles Biomedical Institute, Harbor-UCLA Medical Center, 1124 West Carson Street, Torrance, CA 90502, USA. ibe@labiomed.org
Abdallah
M F
MF
Portugal
A M
AM
Raj
J U
JU
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D000860:Hypoxia; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D016328:NF-kappa B / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects*; D011667:Pulmonary Veins / Q000166:cytology / Q000187:drug effects*; D012756:Sheep; D013329:Structure-Activity Relationship; D014230:Triazoles / Q000494:pharmacology
D001381:Azepines; D005419:Flavonoids; D016328:NF-kappa B; D010972:Platelet Activating Factor; D014230:Triazoles; C063964:bepafant; D018844:Cyclin-Dependent Kinases; D020928:Mitogen-Activated Protein Kinases; D010100:Oxygen; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one