The protective effects of
prostacyclin and its stable analogue
iloprost are mediated by elevation of intracellular
cyclic AMP (cAMP) leading to enhancement of the peripheral actin cytoskeleton and cell-cell adhesive structures. This study tested the hypothesis that
iloprost may exhibit protective effects against
lung injury and endothelial barrier dysfunction induced by bacterial wall
lipopolysaccharide (LPS). Endothelial barrier dysfunction was assessed by measurements of transendothelial permeability, morphologically and by analysis of LPS-activated inflammatory signalling. In vivo, C57BL/6J mice were challenged with LPS with or without
iloprost or 8-bromoadenosine-3',5'-cyclic monophosphate (Br-cAMP) treatment.
Lung injury was monitored by measurements of bronchoalveolar lavage
protein content, cell count and
Evans blue extravasation.
Iloprost and Br-cAMP attenuated the disruption of the endothelial monolayer, and suppressed the activation of
p38 mitogen-activated protein kinase (MAPK), the nuclear factor (NF)-κB pathway, Rho signalling, intercellular adhesion molecular (ICAM)-1 expression and neutrophil migration after LPS challenge. In vivo,
iloprost was effective against LPS-induced
protein and neutrophil accumulation in bronchoalveolar lavage fluid, and reduced
myeloperoxidase activation,
ICAM-1 expression and
Evans blue extravasation in the lungs. Inhibition of Rac activity abolished the barrier-protective and anti-inflammatory effects of
iloprost and Br-cAMP.
Iloprost-induced elevation of intracellular cAMP triggers Rac signalling, which attenuates LPS-induced NF-κB and
p38 MAPK inflammatory pathways and the Rho-dependent mechanism of endothelial permeability.