Anti-inflammatory effects of annexin-1: stimulation of IL-10 release and inhibition of nitric oxide synthesis

Annexin-1 (ANX-1) is an anti-inflammatory protein induced by glucocorticoids. Like glucocorticoids, ANX-1 and derived peptides inhibit eicosanoid synthesis, block leukocyte migration and induce apoptosis of inflammatory cells. Cytokines may possess either pro-inflammatory, i.e. interleukin(IL)-1beta, tumor necrosis factor (TNF)-alpha, IL-12 or anti-inflammatory properties, i.e. IL-4, IL-10. The experiments described in the present study have been performed to answer the question whether the anti-inflammatory action of ANX-1 may be mediated, at least in part, by the release of IL-10. In macrophage (J774) cell line cultures primed with lipolysaccharide (LPS), recombinant ANX-1 stimulated IL-10 release in a dose- and time-dependent manner. In the same cells, the protein and its derived N-terminal peptide (amino acids 2-26) dose-dependently inhibited the release of nitric oxide (NO). Furthermore, both the whole protein and the peptide down-regulated the mRNA expression of the inducible nitric oxide sythase (iNOS). The peptide was also able to inhibit the expression of IL-12 mRNA. These results suggest that some of the anti-inflammatory effects of ANX-1 may be mediated by the release of IL-10, which, in turn, inhibits iNOS mRNA expression and, hence, NO release. In addition, ANX-1-stimulated IL-10 release may also be responsible for the inhibition of IL-12 mRNA expression and, consequently, IL-12 synthesis.