Stimulus-specific regulation of CD63 and CD203c membrane expression in human basophils by the flavonoid quercetin.
BACKGROUND
Flavonoids, such as quercetin, were reported to inhibit histamine release and cytokine production by basophils, but there is no evidence describing their action on membrane markers and intracellular biochemical pathways.


OBJECTIVE
The aim of the study was to examine the effect of several quercetin doses on an in vitro human basophil activation system that evaluates up-regulation of membrane markers in response to agonists.


METHODS
Leukocyte buffy coats from K(2)-EDTA anti-coagulated blood were treated with different concentrations of quercetin and triggered with anti-IgE ("allergy model") and with N-formyl-Met-Leu-Phe (fMLP) ("inflammation model"). Basophils were captured as CD123(bright)/HLA-DR(non-expressing) cells in a flow cytometry analysis and fluorescence values of CD63-FITC, CD203c-PE and CD123-PECy5 were used to produce dose response curves.


RESULTS
Quercetin at a dose of 10 microg/ml strongly inhibited CD63 and CD203c membrane up-regulation triggered by both agonists, but it neither affected cell viability nor changed the expression of the phenotypic marker CD123. The anti-IgE model appeared highly sensitive to the effect of quercetin: a dose as low as 0.01 microg/ml was able to significantly decrease CD63 and CD203c membrane expression. In the fMLP model the dose response was different: quercetin doses from 0.01 to 0.1 microg/ml significantly increased up-regulation of membrane markers, achieving the highest effect with CD63.


CONCLUSIONS
Very low doses of quercetin, within the pharmacological range, inhibit IgE-mediated membrane marker's up-regulation but prime the response to the chemotactic peptide fMLP; this stimulus specificity may have implications on the possible therapeutic action of the flavonoid in different pathologies.
Chirumbolo
S
S
Department of Morphological and Biomedical Sciences-Sect. Clinical Chemistry, University of Verona-University Hospital GB Rossi piazzale AL Scuro 10 37134 Verona, Italy. salvatore.chirumbolo@univr.it
Conforti
A
A
Ortolani
R
R
Vella
A
A
Marzotto
M
M
Bellavite
P
P
D000328:Adult; D000888:Antibodies, Anti-Idiotypic / Q000187:drug effects; D015703:Antigens, CD / Q000276:immunology*; D001491:Basophils / Q000187:drug effects* / Q000276:immunology; D005260:Female; D006636:Histamine Release / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010727:Phosphoric Diester Hydrolases / Q000276:immunology*; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*; D011755:Pyrophosphatases / Q000276:immunology*; D011794:Quercetin / Q000494:pharmacology*; D060149:Tetraspanin 30
D000888:Antibodies, Anti-Idiotypic; D015703:Antigens, CD; C554586:CD63 protein, human; C427944:ENPP3 protein, human; D010980:Platelet Membrane Glycoproteins; D060149:Tetraspanin 30; C026408:anti-IgE antibodies; D011794:Quercetin; D010727:Phosphoric Diester Hydrolases; D011755:Pyrophosphatases