MyD88/PI3-K/NF-κB pathway mediates the antagonism of lipoxin A_4 on LPS-induced synthesis of interleukins in endothelial cells

In order to investigate whether lipoxin A4 （LXA4） has an antagonistic effect on lipopolysaccharide （LPS）-induced synthesis of interleukin （IL）-β3, IL-6 and IL-8 in rat pulmonary microvascular endothelial cells （PMVEC）, and to explore the molecular mechanisms of signal pathway in LXA4 actions, cultured PMVEC were treated with LPS, with or without preincubation with LXA4. Proteins of IL-β3, IL-6 and IL-8 in supernatant were analyzed by enzyme-linked immunosorbent assay （ELISA）. Expressions of mRNA of IL-β3, IL-6 and IL-8 were determined by RT-PCR. Expressions of phosphorylation of phosphoinositide 3-kinase （PI3-K） and myeloid differentiation factor 88 （MyD88） were analyzed by Western blot. Activities of DNA-binding of nuclear factor-kappa B （NF-κB） and activator protein-1 （AP-1） were measured by electrophoretic mobility shift assay （EMSA）. The results showed that LPS induced production of IL-β3, IL-6 and IL-8 in rat PMVEC via MyD88/PI3-K/NF-κB and AP-1 pathway-dependent signal transduction. LPS-stimulated expression of PI3-K, activities of NF-κB and AP-1, secretion of protein and expression of mRNA of IL-β3, IL-6 and IL-8 but not MyD88 expression in PMVEC were inhibited by LXA4 in a dose-dependent manner. In conclusion, LXA4 inhibits synthesis of IL-β3, IL-6 and IL-8 by down-regulation of PI3-K/NF-κB and AP-1 signal pathway in PMVEC.