Effect of kaempferol on IgE-mediated anaphylaxis in C57BL/6 mice and LAD2 cells.

Immunoglobulin E (IgE)-mediated mast cell (MC) activation is crucial in multiple allergic diseases. Parkinson disease protein 7 (DJ-1) and Lyn kinase were reported as the receptor-proximal events in IgE receptor (FcεRI) signals in human MC. Kaempferol, a natural flavonol mainly derived from the rhizome of traditional Chinese herb Kaempferia galanga L. (Zingiberaceae), has been known to inhibit allergic reactions, but it was limited to the receptor-distal signals on rat basophilic leukemia cells. A thorough investigation of the inhibitory effects of kaempferol on human MC has not been done. To investigate the inhibitory effects of kaempferol on IgE-mediated anaphylaxis in vivo and in human MCs, as well as the mechanism underlying its effects, especially the receptor-proximal signals. IgE-mediated passive cutaneous anaphylaxis and systemic anaphylaxis model were applied to elucidate the antiallergic activity of kaempferol in vivo. The degranulation assay, calcium imaging, the release of cytokines and chemokines on the laboratory of allergic disease 2 (LAD2) cells were used to evaluate the antiallergic effect of kaempferol in vitro. Western blot analysis was performed to investigate the DJ-1/Lyn signaling pathway and downstream molecules. Kinase activity assay, immunofluorescence, and molecular docking were conducted to confirm the influence of kaempferol on DJ-1/Lyn molecules. Kaempferol dose-dependently attenuated ovalbumin/IgE-induced mice paw swelling, primary MC activation from paw skin, as well as rehabilitated the hypothermia, and reduced the serum concentrations of histamine, tumor necrosis factor-alpha, interleukin-8, and monocyte chemo-attractant protein-1. Additionally, kaempferol suppressed IgE-mediated LAD2 cell degranulation and calcium fluctuation. Remarkably, kaempferol was found to bind with DJ-1 protein, and initially prevented DJ-1 from translocating to the plasma membrane, thereby inhibited full activation of Lyn, and eventually restrained those receptor-distal signaling molecules, involved Syk, Btk, PLCγ, IP3R, PKC, MAPKs, Akt and NF-κB. Kaempferol could be used as a DJ-1 modulator for preventing MC-mediated allergic disorders through attenuating Lyn activation.