Inhibitory effect of 10-hydroxy-trans-2-decenoic acid on LPS-induced IL-6 production via reducing IκB-ζ expression

The effect of 10-hydroxy-trans-2-decenoic acid (10H2DA), a major fatty acid component of royal jelly, was investigated on LPS-induced cytokine production in murine macrophage cell line, RAW264 cells. 10H2DA inhibited LPS-induced IL-6 production dose-dependently, but did not inhibit TNF-α production. 10H2DA inhibited LPS-induced NF-κB activation in a dose-dependent fashion. In addition, NF-κB activation induced by over-expression of either MyD88 or Toll/IL-1 receptor domain-containing adaptor inducing IFN-β (TRIF) was also inhibited by 10H2DA. Degradation of IκB-α and phosphorylation of IκB kinase-α were not inhibited by 10H2DA. On the other hand, reduction of LPS-induced IκB-ζ expression was discovered. Production of lipocalin-2 and granulocyte colony-stimulating factor (G-CSF), which is dependent on IκB-ζ, was also inhibited by 10H2DA, whereas that of IκB-ζ-independent cytokines/chemokines, such as IFN-β, murine monocyte chemotactic protein-1 (JE), macrophage inflammatory protein (MIP)-1α and MIP-2, was not. Together, 10H2DA specifically inhibited LPS-induced IκB-ζ expression, followed by inhibition of IκB-ζ-dependent gene production. These results suggest that 10H2DA is one of the components of royal jelly to show anti-inflammatory effects and could be a therapeutic drug candidate for inflammatory and autoimmune diseases associated with IκB-ζ and IL-6 production.