Regulation of activity of nuclear factor-kappaB and activator protein-1 by nitric oxide, surfactant and glucocorticoids in alveolar macrophages from piglets with acute lung injury.

AIM

To investigate whether acute lung injury (ALI) in ventilated piglets with bacterial infection affects NF-kappaB and AP-1 expression in alveolar macrophages (AM) and whether nitric oxide (NO), surfactant (Surf), glucocorticoids (GC) affect NF-kappaB and AP-1 activation in AM in vivo and in vitro.

METHODS

The animals were intraperitoneally injected Escherichia coli, which caused ALI. Nuclear extracts of AM were analyzed by electrophoretic mobility shift assay (EMSA) for the nuclear factor-kappa B (NF-kappaB) and activation protein-1 (AP-1) expression. Detection of IkappaB-alpha protein was from cytoplasmic extract by Western blotting. Immunocytochemistry staining was used for intracellular location of p65 subunits of NF-kappaB.

RESULTS

In ex vivo experiments, strikingly higher expression of NF-kappaB and AP-1 by EMSA was found 6 h after bacterial injection in contrast to the Normal group. In the NO, SNO, and GC groups, markedly attenuated NF-kappaB and AP-1 activation was observed. The NF-kappaB and AP-1 activation in Surf group showed lower levels of the expression. Immunoblotting of AM cytoplasmic extract showed low expression of IkappaB-alphaprotein in the Control and Surf groups. The stronger expression was observed in the NO, GC, and SNO groups. AM of the Control and Surf groups showed intense nuclear staining, with decreased nuclear staining in the NO, GC and SNO groups. In in vitro experiment, it caused a significant increase in NF-kappaB and AP-1 activity in AM 1 h after exposure to lipopolysaccharides (LPS). In AM treated by LPS+SNP and LPS+GC, all showed decrease of DNA binding activity of NF-kappaB and AP-1 compared to those exposed to LPS+Surf. Immunoblotting of AM cytoplasmic extract showed that LPS stimulation of AM resulted in the low expression of IkappaB-alpha protein, which was not observed in the presence of SNP and methylprednisolone. However, the surfactant did not show such effect. LPS+Surf-exposed AM had intense nuclear staining, whereas decreased nuclear staining in the LPS+NO and LPS+GC-treated cultures was found, confirming a decrease in NF-kappaB activity.

CONCLUSION

Activation of NF-kappaB was found in AM of ventilated piglets with bacterial ALI. NO and GS could prevent NF-kappaB and AP-1 activation in vivo and in vitro. Surfactant has limited effects on NF-kappaB and AP-1 activity.