Luteolin Is More Potent than Cromolyn in Their Ability to Inhibit Mediator Release from Cultured Human Mast Cells

<b><i>Introduction:</i></b> Mast cells are known for their involvement in allergic reactions but also in inflammatory reactions via secretion of numerous pro-inflammatory chemokines, cytokines, and enzymes. Drug development has focused on antiproliferative therapy for systemic mastocytosis and not on inhibitors of mast cell activation. The only drug available as a “mast cell blocker” is disodium cromoglycate (cromolyn), but it is poorly absorbed after oral administration, is a weak inhibitor of histamine release from human mast cells, and it develops rapid anaphylaxis. Instead, certain natural flavonoids, especially luteolin, can inhibit mast cell activation. <b><i>Methods:</i></b> Here, we compared pretreatment (0–120 min) with equimolar concentration (effective dose for 50% inhibition = 100 m<sc>m</sc> for inhibition of histamine release by cromolyn) of cromolyn and luteolin on release of mediators from the cultured human LADR mast cell line stimulated either by immunoglobulin E (IgE) and anti-IgE or with IL-33. <b><i>Results:</i></b> We show that luteolin is significantly more potent than cromolyn inhibiting release of histamine, tryptase, metalloproteinase-9, and vascular endothelial growth factor. Moreover, while luteolin also significantly inhibited release of IL-1β, IL-6, and IL-8 (CXCL8) and TNF, cromolyn had no effect. <b><i>Conclusion:</i></b> These findings support the use of luteolin, especially in liposomal form to increase oral absorption, may be a useful alternative to cromolyn.