We have tested the effects of combined treatment with a recombinant surfact
ant protein C based surfactant (rSP-C surfactant) containing a phosphodiest
erase-4 (PDE-4) inhibitor, roflumilast, in a lung lavage model of acute lun
g injury. The following groups were tested: (1) controls receiving sham exp
osure; (2) PDE-4 inhibitor (6.0 mg/kg body weight, intratracheally) alone;
(3, 4) rSP-C surfactant (25 and 100 mg phospholipids [PL] per kg body weigh
t) atone; and (5, 6) treatment with rSP-C surfactant (25 and 100 mg PL per
kg body weight) combined with the PDE-4 inhibitor at a dose of 6.0 mg/kg bo
dy weight. The different groups were compared with respect to improving oxy
genation and histopathologic changes, e.g., hyaline membrane (HM) formation
. Both doses of rSP-C surfactant improved oxygenation while even this high
dose of the PDE-4 inhibitor alone did not influence oxygenation compared wi
th untreated control animals. Addition of the PDE-4 inhibitor led to improv
ed oxygenation based on both doses of rSP-C surfactant. The PDE-4 inhibitor
atone prevented further HM formation and infiltration of neutrophil leukoc
ytes. The rSP-C surfactant was able to prevent further HM formation. Based
on both doses of rSP-C surfactant, addition of the PDE-4 inhibitor showed a
dditional effects on oxygenation and inhibition of HM formation. The effect
s of combined treatment were superior to each treatment alone, leading to t
he conclusion that a rSP-C surfactant containing a PDE-4 inhibitor may act
synergistically in this animal model of acute lung injury. We conclude that
combined treatment with rSP-C surfactant and a PDE-4 inhibitor may be an e
ffective treatment for patients with acute lung injury.