Lipopolysaccharide (LPS) is a known inducer of
acute respiratory distress syndrome (ARDS) in humans and animals. In this study, ARDS was developed in rats by intratracheal instillation of LPS and the effect of two types of
surfactant (natural vs. synthetic) was examined to determine their potential corrective roles in general, as well as to compare the two
surfactants against one another in particular, in
endotoxin-induced
lung injury. Sprague-Dawley male rats were divided into four groups, i.e., rats given:
buffer controls; 055:B5 E. coli LPS only; LPS and then porcine
surfactant (P-SF); or, LPS and then synthetic
surfactant (S-SF). In vivo administration of LPS led to an increase in expression of the
cytokines tumor necrosis factor-α,
interleukin (IL)-1β,
IL-2,
IL-4,
interferon-γ,
monocyte chemotactic protein-1, and macrophage inflammatory protein-1β in the lungs of rats. These effects were confirmed by immunofluorescence in lung tissue sections and/or by
protein (Western immunoblot) and
mRNA expression (reverse transcription polymerase chain reaction) analyses of tissue samples. Apart from
IL-4, concentrations of each of these
cytokines in bronchoalveolar lavage fluid recovered from the animals were significantly increased in the LPS-treated hosts. Instillation of either
surfactant (70 h after the LPS) into the airways diminished the expression of each of the inducible-
cytokines, with the porcine (natural) form seeming having the greater inhibitory effect. These data suggest that
surfactant can play an important role in the treatment of
endotoxin-induced
lung injury and might possess robust anti-inflammatory effects. Further, it seems that both the natural and synthetic
surfactants prevent inflammatory outcomes in the lungs by controlling
cytokine(s) production by various inflammatory cells. Last, the studies here clearly indicated that in this aspect, natural
surfactant appears to be more beneficial compared to synthetic
surfactant.