Flavonoids inhibit proliferation and constitutive secretion of human leukemic mast cells (HMC-1) in culture

Mast cells are important for immediate hypersensitivity and inflammatory reactions where they release several vasoactive and nociceptive mediators, as well as cytokines. Proliferation of mast cells is responsible for certain disorders, such as systemic mastocytosis, and may contribute to bladder pathology in interstitial cystitis. HMC-1 cells were grown in multiwell plates in the presence or absence of certain naturally occurring flavonoids which had previously been shown to have anti-inflammatory properties. Here we report that flavone (10^-5M) inhibited HMC-1 proliferation by over 50% at day 3; inhibition at 10^-4M approached 90%, but viability dropped to 20%. The histamine content of the cells was increased by 30% by the third day of growth and was accompanied by morphologic evidence of secretory granule accumulation. The relevant potency was flavone〉 quercetin〉 kaempferol〉 myricetin which had a negligible effect, while morin was inactive. Our results suggest that some flavonoids may be useful in the treatment of certain proliferative mast cell disorders. They are also supported by clinical findings using quercetin as adjuvant therapy for the treatment of breast carcinoma.